Gyralight fans can always visit the B&LE in Ohio and Pennsylvania, where the Gyralights still work on the old tunnel motor rebuilds that lead the ore trains daily. They are bell activated, so they can only be seen in operation at crossings.

These gyrating lights were originally used, as far as I know, in the 1940s. There are references to them in some literature of that time, and at least in early applications, they could sometimes work in different patterns, i.e., either the gyrating "hula" swing most of us know, or a "figure 8" pattern; the latter was in some cases triggered by an emergency air brake application.

One carrier that still used them, at least until relatively recently, was the MARC commuter service out of Washington, DC, and Baltimore, Md. The Gyra-light equipped GP-40 rebuilds have apparently been retired with the delivery of newer MP-36 power, and were sold to the Boston MBTA; other videos of these units in Boston area service seem to have these lights out of service.

http://www.youtube.com/watch?v=hA4myAxGTyM

http://www.youtube.com/watch?v=m0x0jMqZ64g

http://www.youtube.com/watch?v=4hzvd-Kvzik

Like so many other things we like, such as steam locomotives, the Gyra-light was reported to be maintenance-intensive; ditch lights are cheaper.

Check out the light action at 1:06 in this Popular Science short on GM's "Train of Tomorrow" from about 1948; maybe someone can have fun identifying locations as well.

http://www.youtube.com/watch?v=tEfznj0-Ac8

The L&N was a big user of them, especially on their first generation Geeps. They were mounted where the headlings would normally be mounted, with the headlights mounted under them.

The Tennessee Central Railway Museum in Nashville owns an ex L&N GP7 that they have been slowly restoring to L&N paint and configuration. I believe the restoration included the reapplicaton of these.

If I'm not mistaken, this video shows one in active service on a museum line: https://www.youtube.com/watch?v=6gIas6VDwIk

A wealth of information can be found here...
http://www.trainweb.org/gyra/

I love Gyralites. Not surprisingly, it's probably because of growing up next to the Met where the MARC GP40s spent 15 years roaring up and down the line with their Gyralites fascinating me.

I had come into a former Southern Pacific Gyralite, but it was a bit of a basket case that I didn't posses the skills to restore, so it became trade fodder among other railroad junk that was previously sitting in the shed.

Still looking for one to go in the collection.

They're apparently not just for locomotives:

http://www.youtube.com/watch?v=fPHP36JfRB4

Those prices are pretty high!

Ran across this while looking for something else--oscillating headlight on the Nebraska Zephyr, in a nice clip showing this trainset doing what it was designed to do--run fast:

http://www.youtube.com/watch?v=wiNjLHoLuAE

The Burlington applied something that looks like a Gyralite to steam power--in this case, the famous and tragic 5632:

http://www.railpictures.net/viewphoto.php?id=133467

http://www.steamlocomotive.com/union/cbq5632.jpg

In the 1960s, the C&O modified their E7s and E8s with a triangular design I've not seen elsewhere.

http://rr-fallenflags.org/co/co1418ads.jpg

It appears that the triangular mount oscillated side-to-side within the headlight casing.

I'm curious whether the thing still oscillated when the emergency light (at the top of the triangle) was turned on.

Both Mars and Pyle had a model that had a twin beam warning light with emergency light.
http://www.trainweb.org/gyra/specs/20750.htm
http://www.trainweb.org/gyra/specs/sb300.htm

I've seen several roads use them, can't remember which.

Chicago's Metra still uses Gyralites on all locomotives and cab cars: http://www.youtube.com/watch?v=B7IvlEEMS-o.

The agency is presently receiving new "Highliner" EMUs from Nippon-Sharyo, which are replacing the old St. Louis and Bombardier Highliners running on the Metra Electric District. The old EMUs don't have Gyralites; the new ones do.

Figured it worth reporting that the Gyralites contained within the eBay link (big thanks Jeff Lisowski) were given a loving home after playing "Let's Make a Deal" with their seller. A happy ending for all lovers of the Gyra-lite!

Here's some L&N Gyralight action from a restoration a few years ago:

http://www.youtube.com/watch?v=pBkd9GA1ZjI