Yes it looks like a Perry carb that is on "backwards" (just rotate it 180°). The rotating disk is for the low end and it is very sensitive, minute adjustments is the key. The the lines indicate neutral position and maximum points for a leaner and richer settings, yes it doesn't need a larger span than that (!).

The mounting of the backplate is a little compromised but if it doesn't leak then the crankcase damage shouldn't matter.