It's impossible to decipher the engine make based on those numbers. They certainly are not factory stamped. They might be the ugliest re-stamp I've ever seen.
The 914/6 had it engine number stamped on the top of the case adjacent to the oil thermostat. If there is a number up there it might be an original six.
From what you have presented, it still a mystery.
914/6 engine number location.
