Well, I just got back from my second trip there...ha. I picked up the rest of the items mentioned in this thread (and a few of the others; just because). I'll likely be selling most of the stuff I picked up today on here (and possibly GunBroker) once I get it all sorted out.
I'll post up some more pics later this evening when I get time, but for now, here's a little more info about today's haul:
The 37 mm casing (brass) on the left is indeed a M16. The headstamp is: 37MM M16, LOT 15659-40, S.M.C. - 1942. The ring around the primer is stamped: WC 4-7993-23, M23A1 1942
The other 37mm (?) casing is made of steel, appears to have been originally painted a brown or copper color and has no headstamp (that I can see). Has a wrinkle in the neck and a small divot in the case mouth. Other than the length of the case neck and its steel construction, it appears identical to the M16...same diameters everywhere. It's approx. 9.210" tall (~233.934mm)
The USN 1.1" is headstamped "DRILL AMMUNITION" and has 3 holes drilled in the case; steel rod is visible inside (presumably fastening the projectile to the case?)
The slightly shorter empty brass case (referenced earlier as a possible French 25mm Hotchkiss) has all kinds of headstamps. The impression stamps are (starting at 12 o'clock and working clockwise): (12) MR (3) 37 (6) C and (9) 2. It also has several ink stamps on the headstamp area; they're hard to read, but I think they say: H25.13.??.3L HR.10.5.9.38. Again, not sure on half of the ink stamps; they're pretty light in areas. There's also some ink stampings on the outside of the cartridge, but the only thing I can make out is "CHARGE" stamped in 2 places; 180 degrees apart. It's roughly 7.66" tall (~194.564mm), 1.858 rim diameter (~47.1932mm), 1.681" diameter nearest the rim (~42.6974mm), 1.533" diameter at the bottom of the shoulder (~38.9382mm), and roughly 1.043-1.063" outside diameter of the neck (~26.7462mm; the neck is split and pretty beat up).
The Lahti round is live, and is headstamped: 1939 TIKKAKOSKI with a "T" inside of an upside-down triangle, inside of a circle between the "19" and "39". No noticeable markings on the bare steel projectile.
The Davy Crockett spotting cartridge (no projectile) is ink stamped "20MM SPOTTING, XM101, LC2-29" on the side of the cartridge case. No headstamp and a very weird looking primer. It appears as if the primer is removable / replaceable with a spanner wrench.
The cartridge thought to be a Japanese AA round has 2 small (barely noticeable) markings on the headstamp pad; they don't really make any sense, so I'm going to assume they're Japanese characters...lol. However, I don't believe the projectile that's in it is correct. The projectile is stamped, "MK.XXV?? MOD...MBCO.LOT" on the copper (brass?) fuze and "MK3-54J, LOT 1192, MAT" on the steel body of the projectile. The main body is painted O.D. green and the fuze is bare. There's one driving band made of copper (brass?)
One of the M21A1 cartridges (with the all-black projectile; original paint) is headstamped "DPS 1942, 20MM M21A1" and the projectile is stamped "LOT-52354-11, 8-42" with some sort of symbol stamped above the LOT#; it kind of resembles a capital "G" with something in the middle of it. There are 2 holes drilled in the case with a piece of wood visible inside.
On the other M21A1 cartridge (black projectile with red band near base) is headstamped "S.M.C. 1945, 20MM.M21A1" with no markings visible on the projectile (no holes drilled in case either)
On another 20mm cartridge (plain steel projectile) is headstamped "BBC 1941 20MM" with no markings on the projectile. It appears to be roughly the same size cartridge case as the other 2 M21A1's
Until I get some pictures up this evening, can anyone provide some more insight on my finds?
-WRM