needs to stick with a standard format
I agree. It would be nice if all coins of a specific Face Value had a similar form factor. That would allow the completionist geeks among us to keep our OCD under control.
If you look at the FV of $25, it has been used for 40mm, 60mm, 38mm, 36mm, 34mm and 27mm not to mention a football shaped coin and some high relief coins where the thickness causes issues with a tray. Were you a collector of $25 with a desire for a common display then you are into designing and building a custom presentation cabinet of some form... not something off the shelf.
$30 doesn't fare much better... It commenced in 2005 with a 40mm coin then in 2014, a 54mm coin which stuck until the Zentangle series were issued at 50mm.
The $1 SD has been a stalwart at 36mm (+/-) since 1935 with few diversions... notably the introduction of the nickel $ at 32mm then the Loon at 26.5mm. In the NCLT realm, ignoring the "big Coins" all SD's have fit the 36mm diameter with the exception of the two loons issue at 38mm in 2012. The weight of the coins has fluctuated but that has been accommodated by thickness and minor diameter changes not a form factor adjustment. This year the RCM
has decided to give us the High Relief $1 Peace coin and a 34mm Piedfort 1949 reissue. I hope this is not a trend going forward.
Another series I collect is the $100 gold. That has been 27mm since 1976 (excepting the 1st 22k version) and has remained through karat changes and weight reductions... This year though we got the Apollo 11 coin at 25mm and convex format... I passed.
Not that I don't want these coins to be produced... just not in the familiar $1 or $100 formats.