If you have the circular shaped side load bowl then it should be a Monobloc. The concentric types were common replacements in the later 60s & 70s since they were all that was available new. The Monoblocs were made in all sorts of configurations from single carb installation to twin carb and some twin carbs required narrower float bowls to fit close enough on some models of bikes. You may have one from a twin carb installation that the other mate had the air valve. It's just hard to say. If it works OK without the choke, you might as well use it the way itis until a better deal comes your way. As was mentioned before, it might just need the valve and a twin spigot top to convert it to air valve type but it depends on which innards it has. Some have the inner metering body parts that don't have provisions for an air valve so that part may also need to be replaced. The new carbs that are available from Burlen fuel systems are not cheep so a guy on a fixed budget might have to get by the best way possible for now. I see them on E-pay now and then but there is no way to now whether they might need a new slide or need to be sleeved due to wear. All options cost money so it's always a risk with used parts.