This Japanese manufactured rear butt stock sling swivel mounting screw with the finer thread is for the Type 38 Arisaka bolt action rifle in 6.5 caliber and is in good condition exhibiting a brownish gray patina with some rust and light slot wear.  (file photo)

Note: Japanese Type 38 Arisaka bolt action rifles with the following arsenals and serial numbers have been observed with this part:

Koishikawa / Kokura: 00206, 00103467 & 887486