You have what is commonly referred to as an OB-410 though there were several model #s that covered them. (A-410, 411, 431, etc…) I don’t recall if the model # was stamped on them, I want to say it was unobtrusively stamped on the transom bracket somewhere. Regardless, all the OB-410s were pretty much the same with only differences I’m aware of being the tiller pivot and lower unit shape. They were made from 1940 to 1947 and rated at 2.5hp – all are a 4-stroke design.
The tank on your motor is from a later S-300 model as is evident by the starter mounts (I don’t think any of the OB-410s had recoils) and the beige paint showing through. (The tanks were pretty much the same save the starter mounts) It also looks like someone changed to the later recoil rope plate.
They are decent running motors and worth restoring. You have the rear motor cover, something that is missing about 50% of the time. All of them I’ve come across also seem to be covered in house paint, they should be all silver hammertone from top to bottom with the decals (American Outboard is a source for them) as the only color. While not as smooth or quiet as a Johnson JW, at WOT the Lauson OB-410 won’t quite rattle the fillings out of your head, or deafen you like a swarm of angry wasps, as so many other small 4-cycles do. They are very pleasant at less than 2/3 throttle and will idle all day almost silently.
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