Great start guys. Sorry to be the holdup. I know this has been a long time in coming, and I hope you will soon understand why . This part of my posts to this thread will be limited to the reduced folles (aka nummi) issued for Helena. I will be adding a separate listing of styles and mints for the AE4 posthumous coinage in her honor as issued later by the heirs of Constantine. More on that at that time.
If we may count my earlier display for Galeria Valeria by mint as the first Women of Rome "style show," my first contribution to this thread for Helena will be a style show of her hairstyles on the reduced folles for the various mints; i.e. 14 of 15 with the exception of London. All but one of these will be of the
SECURITES REPUBLICE reverse type. The obverse design for each of these is a variant on a common style designated by Patrick Bruun as "E10" in RIC VII. Its details will be set forth below. Within each mint the coins are here arranged chronologically by series* but only where the bust design showed a noticeable difference in hairstyle. Many of the differences are quite subtle, within a mint as well as between mints, but in some cases the styles are quite distinctive.
....*Series dates are differentiated by style of mintmark.
A Word about Order
Mints are listed from west to east following the order in RIC VII. In each case I indicate the range of dates coins were produced for Helena at that mint, then note the number of production series known, and give the catalog numbers for any entries missing from this display. Then I show the entries for each series in chronological order and give the catalog reference, mint mark characteristics, and date of issue for each coin shown. I use written comments to call attention to specific features.
By this listing I hope list members can more easily recognize when they have a design type not yet listed here and add it to our "collection." My hope is that this will stimulate you to seek out good examples of the missing coins and bring them to our attention. In any case, please add whatever examples of these reduced folles you have, and tell us about them.
All the coin images in this post were taken by me of coins in my collection.
Londonium/London (324-325)(missing: RIC299) One series issued, seldom in market
Lugdunum/Lyons (324-325)One series, as here. Her hair is simply combed back and combed under at the base, then secured with a banded diadem with a ladder-like segmentation. A row of bangs hang across the front below the diadem.
RIC 234 (PLG) 324-25
Treveri/Trier (324-328)Missing:RIC458, 465, 515
Two of five series represented here. In both of these the hair appears to be covered by an open cap with a high well defined crest, and a prominent base which might also serve as a diadem.
Series 3: Our first example is from the third series, in which the crest resembles a laurel band with an arc of pearls beneath it. The hair has only a shallow loop at ear level. The diadem is banded with two rows of dots (pearls).
RIC 481 (STRdot/crescent) 326

Series 4: Here the crest appears as a cap with laurel decoration and bounded by pearls all around. This "cap" extends down the neck to the ear and forward beyond the diadem. The diadem is a plain band with a row of pearls in it.
RIC 508 (STRE) 327-28
Arelate/Arles (324-329)Missing: RIC278, 317, 324, 340
Series 2: Hairstyle, not crested, curves around to the neck, with "ladder"-style band diadem, with or without dots, and bangs grouped below the diadem.
RIC 299 (TAcresentRL) 325-26

Series 3: Same hairstyle as series 2.
RIC 307 (S F/TARL) 326-27
Rome (324-326)Missing: RIC270
Series 2: coarsely braided crest arches over other hair to back of neck and curves back to ear. Diadem band "laddered" with dot in each cell. Rosette centered in front.
RIC 291 (RwreathQ) 326
Ticinum (325-327)Missing: RIC209
Three series with high arching crest and simple diadem.
Series 1:Moderate double crest of braids arches to diadem, below is a looping queue. Grouped bangs across front. Diadem is a single strand of pearls; no front decoration. Earring.
RIC 190 (TT) 325

Series 2: High double crest of braids arches to diadem, below is a looping queue. Grouped bangs across front. Diadem is a single strand of pearls; prominent rosette; grouped bangs below diadem. Earring.
RIC 202 (QcrescentT) 326
Siscia (324-329Missing: RIC 187
Of four series the first two are only represented in RIC by a single coin each. We begin with an unlisted example from the second series.
Series 2: High arching double crest of braids (waves of curls?) above a third wave, all above single strand of pearls, ends in a short queue below ear. Simple bangs below diadem.
The mark style was represented in RIC by a single example, only for officina E.
RIC 196 (ASISwreath) 325 --not listed in RIC

Series 3: Hair combed back without crest, bobbed in a queue at back below ear. grouped bangs below diadem. Short banded diadem with a single row of small, widely spaced dots.
RIC 204 (.ΓSIS.) 326-27

Series 4: Same as series 3 except for a pronounced loop of hair in front over diadem.
RIC 218 (ΓSISdbl-crescent) 328-29
Sirmium (324-325)Single series with hair combed back without crest, bobbed in a queue at back below ear. grouped bangs below diadem. Short banded diadem with a single row of small, widely spaced dots. (compare Siscia)
RIC 60 (SIRM) 324-25
Thessalonica (318; 326-328)The earliest Imperial bronze reduced folles/nummi in honor of Helena begin in Thessalonika in 318 with the distinctive "star in wreath" reverse type. This preceded her elevation to Augusta (324) and marks her elevation to the lesser status of
Nobilissima Femina (
N F on the obverse). The obverse bust is very distinct from the later series, inasmuch as her hair is combed straight back and secured in a chignon at the back at about the level of her ear. There is neither diadem nor a row of bangs in front.
RIC48 A6 318-19

Though honored in gold at her elevation to Augusta in 324, there is no more bronze for her until 326 when Thessalonica joins the other mints in issuing the SECVRITAS REPVBLICE reverse type for her. Although this continued in production for two years, only one series was produced.
Officina 3: the hair is combed up slightly and back, with no crest. The diadem is a "laddered" band with curved crossbars and a dot in each segment.
RIC 159 (SMTSΓ) 326-28

Officina 5: the hair is combed back in large circular arches, but with no crest. The diadem is "laddered" with a dot in each segment.
RIC 159 (SMTS
ε) 326-28
Heraclea (325-330)Missing: RIC109, 110
Here are the first three of five series from Heraclea having an issue for Helena.
Series 1: Finely combed high arching twisted queue arches over her hair front to back of the neck and takes on a flat bottom at the level of her chin. Tight curls hang below the diadem in front. In this series the diadem is a simple band with large dots.
RIC 79 (SMH
ε) 325-26

Series 2: combed hair front to back without crest or queue. Tight curls hang below the diadem in front. The diadem is a simple band with a single row of small dots
RIC85 (SMH
ε.) 326

Series 3: Three braids arch front to back over combed hair and are tied up in a rounded queue at the back of the neck. Tight curls hang below the diadem in front. The diadem is a simple band with a single row of small dots.
RIC89 (.SMHΔ) 326-27
Constantinople (326-327)
Only one series, from the only two officinae that produced them. The slight differences in the appearance of the hairstyle may only be due to wear and not design.
Three braids arch front to back over combed hair and are tied up in a rounded queue at the back of the neck. Tight curls hang below the diadem in front. The diadem is a simple band with a single row of small dots.
RIC11 (A/CONS) 326-27

Two braids arch front to back, otherwise as above.
RIC11 (B/CONS) 326-27
Nicomedia (324-329)
Missing: RIC 95, 159
Four series of coins were issued for Helena. Shown here are the second and third series, arranged by date. For these her hairstyle is typically crested with a line of pearls, banded or unbanded, as a diadem. Details of the diadem decoration vary.
Series 2: crested with simple string of pearls as diadem. Bangs in front.
RIC129 (MNΓ) 325-26

Series 3: crested with band of pearls as diadem. Grouped bangs in front.
RIC148 (NΔ) end326-27
Cyzicus (324-328)Cyzicus issued coins for Helena in four series, shown here.
Series 1: the top crest is represented by feathery strokes pointing back, as is the hair above the band of pearls, which is represented by a single string. Her hair hangs in bangs below the string of pearls
RIC28 (SMKΓ) 324-25

Series 2: the crest appears as wisps of hair combed back. The hair above the band appears as short vertical strokes, but the band is a double row of mounted pearls. Her hair appears as horizontal waves below the band.
RIC39 (SMKA.) 325-26

Series 3:
(at officina gamma) the top crest is represented by arched strokes pointing back, as is the hair above the band of pearls, which is represented by a single row of mounted pearls. Her hair hangs in bangs below the band of pearls
RIC49 (.SMKΓ.) 326-27 (dbl dot; off 3)

(at officina delta); the style is very similar to the first series: the crest is represented by strong strokes pointing back, as is the hair above the band of pearls, which is represented by a single string. Her hair hangs in bangs below the string of pearls
RIC49 (.SMKΔ.) 326-27 (dbl dot; off 4)

Series 4: All the hair above the band of pearls is brushed back slightly, with no crest. Below a single row of mounted pearls her hair hangs in bangs.
RIC54 (SMKΓ/dot) 327-28
Antioch (325-329)
Missing: RIC61, 75
Reduced follis/nummus coinage for Helena started with an anepigraphic type in 324. This was replaced in 325 with the E10 obverse bust and SECVRITAS REIPVBLICE reverse, which continued in production into 329. Hairstyle design sequence types:
1-single or double row of dots; hair-crest
2. diademed
a. band diadem, plain or row of dots (no bars); hair crest
b. ladder shaped diadem; usually w/o hair crest
RIC67 (SMANTA or B) type 2b 325-26

RIC82 (.SMANT/Δ
ε) type 2a with dots; 328-29
Alexandria Missing: RIC 44, 53, 57
Bruun in RIC VII describes the hair on the busts from this mint as "Magnia Urbica" fashion for all five series. (See images in index thread for Magnia Urbica)
Series 1: barest treatment of crest, main hair, and tail; single strand diadem
RIC38 (SMALB) 325-26

Series 3: hair strands well defined with crest; band diadem with single row of dots
RIC48 (wreath/SMAL/A) 327-28

Series 3 (variant?): Although the hair is less defined, as in the first series, I think here that may be attributed to manner of execution and preservation.
RIC48 (wreath/SMAL/A) 327-28

Here it must be admitted that the sample of examples for each of these varieties is not sufficient to be at all conclusive about the original forms and variants. These results must be seen as preliminary. Nonetheless, these ARE examples of each of these types, and may set down general parameters for what to expect.
This completes the images for the reduced folles of Helena. Do you have a favorite?