I've got a pretty good mic collection myself. Must be around 200 or so mics now, with a few doubles.
I started to collect when I was renting a warehouse from Maryland Sound. My neighbor was a vidio playback guy (He hooks up to the film cameras on location and records the takes on video. Then the director can review the scene and decided which takes to actually print to film. Cheaper than printing every take to film for later review) and had a side business. He also rented out vintage and antique TV sets to the video and movie industry. Some of the sets actually worked, while many others had no screens or CRT tubes. In use, a modern video monitor was placed behind the antique TV's glass and made to look like an operating TV.
We got to talking one day and I discovered that the movies always needed strange props like old microphones, TVs, Radios, Cameras, etc. I got hooked and started to collect old tube table radios, old home style picture cameras (like Brownies and Poloroids) and of course, old microphones.
Over the years I only rented one radio for a shoot (used in a commercial) but I started to rent a bunch of mics for comercials and films. I never really got into the cameras, and ended up selling most of my camera collection to a guy in town who was an avid collector. I liked the radios, but I was running out of places to store them (I had about 100 radios at that point) and I also sold many of the older wooden ones to a collector. I kept a few of the art deco and bakelight models because they are so neat looking (I also kept a few that are worth serious money, and will sell them someday when I need to pay the monthly rent at the old soundman's nursing home)
But, being an audio nut, I kept collecting mics. At first, I would buy any mics that looked neat and were in good cosmetic condition, working or not. Then I started to specialize in mics that were mainly used for live PA and had a built in stand socket. (think the EV 664 or Shure 555) Now I'm back to collecting any type of mic that looks neat or different. I collect all brands of mic EXCEPT RCA! I find that they are too exspensive, and other collectors will pay outrageous prices for even beat up models.
I get a lot of my mics on eBay, but I also find a lot of them at flea markets, pawn shops, antique stores, and Ham fests. A Ham fest is an amatuer radio flea market. Great place to pick up old parts, and odds and ends!
Lately I have been going after boom mics (mics that are used in tv and movie production and used on large mic booms suspended over the talent) Here is a recent buy from eBay. Its the EV 642 Cardiline Mic. Its the second of this type that have now, but this one came with the warranty registration cards and booklet (booklet not shown in pic) The two holes on the body of the mic are to adjust impedances (50, 150, 250 ohms) and to adjust frequency response (flat, curve 1, curve 2) In use it would be mounted in a shockmount and attached to a boom stand.