So this is an old thread but I found a set (4) of these or something similar going by the picture. Mine don't seem to have any visible model number on them and this thread is about the only thing that pops up when you Google "Leonhardt Englneering speakers". But a business phone number also turned up. So I called it.
A really, really nice but very, very old man answered. He must be the Leonhardt of Leonhardt Engineering and might be all that's left of the company. He was clearly hard of hearing, so it was slow conversing but I did manage to get a little bit of information out of him. He said it had been 40 or 50 years since they stopped making these. He didn't tell me much about the specs but did manage to remember that they took 1-A fast-blow fuses (important for me because, while I did get all 4 working, I had to do it by rotating the one non-blown fuse through each speaker). He also mentioned they had a hard time selling them as dealers didn't like them, which he said was because they cost a fraction of what speakers selling for $300 and $400 at the time did yet sounded every bit as good. I have no reference for that. These aren't amazing by any stretch of the imagination, but they sound pretty decent and, as they are super rare, are kinda cool.
It's not much from a technical standpoint but thought I'd add it in case anyone else comes across a set of these and wants a little info.