The Milburn Cub was just one of many companies/names that built your small single cylinder air-cooled outboard. It was produced from the late 1940s to the 1970s and available via mail order. In the course of production they were sold under several names: Budbuilt, Comanco, etc…. Milburn being the name that seems to have stuck to the whole line.
I believe the Milburn versions were made from about 1948 into the early 1950s. They produced two models, the standard had underwater exhaust, 360 degree steering and thus reverse. The Deluxe version (that was like $6 more!) had a pipe ducting the exhaust underwater but negating the 360 steering. (This is the opposite practice to most every other outboard maker). Most of these motors were painted with bright red (these days it appears to be a grubby brick red) wrinkle finish on the tank and dull aluminum leg and powerhead. I’ve seen a couple that had bright green tank.
Take a look at the crankcase casting under the tiller and you should find a better number, if I recall, the first digit or two correspond to the year (i.e. 49 = 1949)
Of super simple design and downright terrible quality, there are people who really like them since they are so far out of the ordinary!
Here’s a photo of where the serial # is on the ones I have:
