I'll chime in at MS65 RB, because from the photos I don't see any clues as to why this
IHC got a PF...no shine at all in the fields and no matte finish as seen on other
IHC proofs, so I'll go out on a large limb and hand you a chainsaw--it's a Pattern/Test coin--much more unique and rare than a proof!
It's unfortunate that you can't weigh the coin, although PCGS might be able to give you the exact weight in grains of the OGH for small cents and you can then do the simple subtraction from total weight. I have an 1863 bronze
IHC that is clearly one of the bronze Pattern or Test coins mentioned in Rick Snow's 1st Edition in 1992 (with an R8 rarity of 1-3 pieces), as it's a very THICK planchet and it weighs in @ 74.2 grains. It's visibly thicker than any 1859-1863 Cu-Ni, yet the bronze alloy has a lighter tone (more white/yellow) than the later bronzes of 1864 onward, and is
CLEARLY more red than a Cu-Ni. I've seen descriptions of patterns in 1863 struck in Aluminum, Brass, and another blend of bronze alloy--one different than the final alloy mix of 95%Cu;3%Sn;2%Zn. This appears to be one of them.
It's off to Rick this month for attribution--because it has additional traits worthy of note: a hub rotated
DDR (CW 2-3 degrees,) an offset hub
DDO (to the NE approx .5mm,) and a RPD to the west (1863/8) that's visible inside the lower loop of the "8" on the left, as well as a slight amount in the upper loop--not a currently named Snow variety of the RPD in an 1863. I can't stop looking at it! I plan on posting the results of Rick's review in addition to photos after it returns from Arizona.