mystery (to me) "Radio Altitude" gauge

[mennie]

Hi,
I found this on eBay 2 minutes before closing so I thought let's try and bid. I won it for US $10.50.
But what is it? How would this be operated? (Not that I'm going to try and hook it up to something)
It might not even be something that belongs in a P-51?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120013616748

Vintage General Electric GE Model 8D039AAA2 IndicatorReq # C-70Y716 Serial # 2308053 Date Feburary 1945. Face is marked Radio Altitude / Hundred feet with a 2 setting Range Switch & On/Off Control.

[Don Martin]

Radio Altimeter
Lloyd Espenschied invented the first radio altimeter in 1924. In 1938, the fm radio altimeter was first demonstrated in New York by Bell Labs. In the first public display of the device, radio signals were bounced off the ground, showing pilots the altitude of an aircraft.

[Dan K]

Mennie,

What you've got is the altitude indicator of the AN/APN-1 radar altimeter system. It's a terrain clearance altimeter, having two ranges, 0-400 feet and 400-4000 feet. Instrument would be found in most late-war naval patrol and bombing aircraft.

[mennie]

Thank you!
I found more information now, googeling.

AN/APN-1
Radio Altimeter (improved AN/ARN-1); used in P-61, C-119, B-32, C-121, H-19, P-5, AF-2W, AD-5, F2H-2/2N/2P, F3D, F6F-5N, F9F, XF10F-1, P2V-4, PB4Y-2, PBM-5S, PBY-6A, R5C-1, R5D-2, R6D-1, SB2C-5, TBM-3S

Not on a P-51 as I hoped but I already thought that.

AN/APN-1
Radar Altimeter, 420-460 MHz, Doppler frequency shift, dual scale meter 0-400 and 0-4000 feet, TO AN 16-30APN1-4, Output 0.1 W, 14 or 28 VDC, Major components

RT-7/APN-1 Transmitter-receiver,
2 ea AT-4/APN-1 antennas
ID-14/APN-1 Altitude indicator,
SA-1/ARN-1 Altitude limit switch

Still it can be a good looking gauge for little money.

[mennie]

I received the item today; it seems to be in excellent condition.
The switches are still operational, looks new except for some light tarnish.