Classic RCA Type 77 Mic Knockoffs
If you look at album covers from the 50's and 60's, you'll often find artists crooning into an RCA Type 77 microphone. It's one of several microphones who's silhouette has become iconic of recording, and even of music itself. The 77 deserves its reputation, but it also got what it didn't deserve, loads of cheap knockoffs.
Pictured here is my Olson M-102. As you can see, it's rather lovely. When people see this mic on my desk they really, really want to record with it. The problem is that, like so many other Type 77 knockoffs, it sounds just awful. The knockoffs retailed for anywhere from US $15-30 in the 1950's. While the RCA original is a fine recording instrument, the cheapies mostly had inexpensive mic elements built in. Perhaps the lack of quality went unnoticed in some of the home recording gear of the day (to be fair, the mics were intended for the ham radio and PA market), but today these copies bring nothing of the vintage sound that people go for.
The upshot is that a smart buyer can pick one of these up pretty easily starting at $10 (I think that mine was actually $6). At the same time, I've seen these knock-off versions go for unreasonable sums because the buyer doesn't realize what they're getting into. So be careful. If you're looking for a good-looking prop microphone to put on a desk, this is perfect. I've heard of some folks buying one of these mics cheaply, then adding their own new electronics inside to build a custom microphone who's sound is worthy of its outer good looks.
Just remember to take care when you search for "vintage microphone" on Ebay. I've linked to a list of the knockoff models which will aid you in your search. You can sing our praises later. Just promise that you'll use a better microphone, okay?