The question about the hole has been answered in your other thread, it is for a kickstand and features on a lot of imported frames.
However, it is not a Motomag as it is a mk2 frame with the revised rear drop-outs. It is just simply a Mongoose. At the very end of the run of these in 1983 that my became known as Californian but either way it has chromo main tubes but a hi-tensile rear end
As said on your other thread, get a wanted ad up for a UK based one as the import duty will surprise you just when you thought you had a bargain
Spen
Ps - i taught Bobafett all he knows.....