1988 Trailboss need help with a part number

Recently picked up a basket case 1988 Trailboss 250.

It was leaking case oil out the back of the crankcase. There is just a bolt straight missing… lol

Anyways it looks like its a check bolt, to check the fluid level, and I can’t seem to find anything close to it on schematics.

Anyone have idea which bolt I’m talking about?

Thanks guys!