FWIW, Bill, I would agree that if you plan to continue to use your heirloom M3, a close match would be a good idea. If, however, you're thinking of keeping it safely stored at home, other options (and the operational differences) would be less of an issue. In that case, you might consider the greater versatility of something like an M6TTL for not much more than you'll pay for an M3 in good condition. (Yes, there's a battery for the meter, but they last a long time, and a spare is easy to carry.)