Japanese Arisaka rifle (Arisaka-ju, 有坂銃) Type-99 7.7mm rifle.  This example has  a defaced (filed or ground-off) kikukamonsho (菊花紋章) or Imperial chrysanthemum ('mum') crest or stamp, often found on rifles surrendered post-15 August 1945. (Photo courtesy Lawrance Ordnance Pty Ltd, Australia.)

Arisaka-Type-99-7.7mm-'mum'