looks like a model 45 to me from that tiny pic.
take of the chain guard and see if the chain is still attached, then start the thing up, and engage the clutch to see if its spinning.
its most likely a worn clutch plate, which you can replace easily for about $5.
you can also adjust the clutch by tightening the bolt where the clutch cable goes, you'll need to take the chain guard off for that sine the bolt requires you to hold one end while turning the other.
