The kind of advertising you simply don't see any more, sadly. This particular sign is an absolute cracker too, in terms of size it's large, very large. It's all very patriotic and very sixties with the giant Union Flag but it pre-dates that particular decade by thirty or forty years.
Now, one of the amazing things about it is that there are are no airgun pellet or .22 indentations in the enamel so it would seem that it wasn't a sign from a country garage or rural area. Plinking signs for target practice was, and probably still is, a very rural pursuit.
They don't make them like that anymore and by that I mean enamel advertising signs, not targets.