Is it a split buss panel? It appears to be one but my monitor leaves much to be desired,if it is it would explain the main lug kit instead of a breaker,but I count 5 mains. Some of the most obvious violations are: double lugged conductor and unprotected also.The SE cable below the main lugs, I assume is supplying another panel?
The "workmanship" and the "quality" of the panel go well together : Very poor,the damage at least will mean that it has to go.
PS 384-16 (a) all the way back to the 1965 NEC says no more than 2 mains in a panelboard, the change occured in that edition,but there was some tweaking of the exceptions over the years since.