Looks like it to me by the seat latch. Original seat pattern would have been a sign but its recovered. It's a '71 so probably is a K0 (but not one of the early crankcase ones). But I am still learning on these.... Trigger's your man or Bryan. Think the K0 has small reflectors too.
This is what the 'York Guru' told me:
"There are some parts specific to your 500/4. The rectifier/ regulator has a square plug where the K1 is rectangular. small reflectors on the headlight ears. Thinner kick-start rubber. The seat and seat locking mechanism, the on/off is in the switch gear as opposed to the K1 separate switch. The lifting rod on the carbs was thinner. Honda Motos Co sticker under the side panel badges, metal coloured carb and airbox round clips where as K1 were black, different handlebar grips – thinner ribbing. Engine numbers start with a 1 ie CB500E 1********"
