Find that Philco

 

Are these all Philcos? No. I just like the alliteration. This dial lists KOA, KGIR and all the other buttons are knocked out. That's not a lot to work with. 850 KOA-AM signed on in 1924. They signed on as a 5,000 watt station and in 1927 increased to 12,500 watts, becoming an NBC affiliate in 1929. The station was so ubiquitous in that era it does not narrow the date range. 

Today the KGIR-AM calls reside in Cape Girardeau, MO. But back in the 1930s, KGIR was a 500 watt station in Butte, MT on 1360. With only 500 watts of power, I think that puts our radio somewhere between Butte and Cody, WY. They're about 500 miles from Denver, but surely able to receive a clear channel station in that era.  The station signed on in 1929 and changed its call letters to KXLF in 1946 which book ends our date range.

Here we have a more to work with, though the labels have slid around unhelpfully: KMPG?, KOH, KGMB, KGKB, KROV, and KICA. But what a weird selection. 590 KGMB I can hardly believe as it's was based in Honolulu. It also can't be KGME-AM in Phoenix, AZ. It signed on in 1940 on 1200, as KPHO only picking up the KGME call letters in 2000. I hope I'm misreading that one. KROV does not exist that I'm aware of. I think that could be KRGV in Oroville, CA but more likely 690 KROW in Oakland, CA which used those calls from 1936 until 1964 before it changed to KABL.  More here. 

980 KICA-AM was most recently a farm station in Clovis, NM. The calls are not cut off. But earlier it was a TV station with the same calls in the same city. It was on 1240 back in the 1940s, and 1370 in 1936. This is highly unlikely with it's distance from the other bay area stations, but I have no other plausible matches. 

630 KOH-AM was not in LA, it was in Reno, NV from 1928-1994 when it became KRCV-AM. The stick on 780 in Reno is KKOH, it borrows the brand name but is not otherwise related. The original KOH, now KPLY is known the oldest radio station in Nevada. 

The first calls are KMP-something. Station 710 KMPC-AM was in Los Angeles. More here. The calls have moved around and currently broadcast Radio Korea on 1540 in LA. The original station first signed on as KRLO in 1927 and changed calls to KMPC in 1930 and held the calls for 67 years. Gene Autry owned KMPC in the 1950s. It aged with it's audience and was Adult Standards and talk radio in the 1980s.  

Just one more. This one is fun with the vertical station levers instead of push buttons. I see KGFW, KFAB, KMMJ, WGN, and WOW.  KGFW, is another heritage station, founded in 1927in Ravenna, NE. The station moved to Kearney in 1931 where is remains today on 1340. KFAB is even older and first signed on as KFRR in 1924. It moved to 770 in 1928. 

KMMJ is almost as old, having been founded in 1925 in Clay Center, NE. Noe how near Kearney that is.  I think 720 WGN-AM out of Chicago is an outlier, received only because it's a clear channel station.  Likewise 590 WOW has been on air for 100 years but never more than 5,000 watts. I think this radio sat between Omaha and Grand Island. This set of stations is pretty consistent. 

the extinct Mobile radio license

It is unimaginable now, but in the early days of broadcasting, it was possible to operate a legal broadcast from a moving vehicle. Not a relay to a stationary transmitter, but to originate programming, perhaps even while steering.In 1919 I find the earliest reference to a license to broadcast from a car. Alfred H. Grebe broadcasted from both cars and boats with the call letters WGMU. Grebe manufactured radios. the purpose of the traveling radio show was of course... to sell them. they were nice radios, usually a chassis of Bakelite and/or nice hardwood like walnut. Alfred was from Richmond hill NY born in 1895. He aso founded WAHG, WBOQ, and other less formal stations right out of his factory in Queens. More here
His mobile station used a 6-wire flat top antenna but it was hardwired to the frame and body of the car! It operated at 150 meters. He did observe the the spark plugs of the other motor vehicles caused interference even then. In advertisements he called it the grebe Auto Radiophone. Grebe said in a Radio Amateur News article:

"The auto-radio-phone is entirely practical, and the near future should bring extensive developments along these lines..."

In the late 1920s Jay W. Peters was broadcasting in Inglewood, CA as 1470 KGGM. Then in 1927 he loaded his transmitter with a collapsible antenna and moved to Albuquerque, New Mexico. I've also seen images with a rig attached to a bus! He too was demonstrating radio equipment that he was trying to sell. Peters traveled the Southwest doing demos. In 1928, he sold the license to the New Mexico Broadcasting Company. In 1928 he moved to a terrestrial stationary radio license. He went to Reno and tried to start another station near Blanch Field Airport in an Elks lodge. He applied for a license, and got the calls KOH. it was the first commercial station in Reno. More here.