This bayonet is very different from the original US M1 Garand bayonet and was was designed to fit the US M1 "Garand" Infantry Rifles used during the Korean War. It is believed this type Garand bayonet - with large push-button - was designed and adopted to be used with large gloves as in the colder Korean climate. The US M5A1 is virtually identical to its predecessor, the US M5 Garand Bayonet.

Blade is unmarked, but underneath the cross-guard is K-M5A1, alongside what appears to be an arsenal stamp; this mark perhaps is Korean and looks like an exaggerated hourglass. I presume these were either period-made in Korea or in the US then subsequently issued to Korean troops.
Black plastic grips, iron mounting (steel), steel Parkerized blade.

Scabbard is olive-drab fiberglass body with steel throat and drag. Throat is stamped USM8A1 / PWH. This is the correct scabbard for all the bayonets - and knives - of the M3/M4/M5/M7 style.