1920s Kellogg RFL electric radio set questions

Dear All,
I am about to come into possession of a Kellogg RFL (Radio Frequency Laboratories) tube radio. This an early household current powered coffin-box style radio from the 1920s that requires an external horn  or cone loudspeaker. The radio also uses the McCullough tube where you connect two wires to the top of the tubes after plugging then into the tube sockets.  My question revolves around the fact that I read that this radio is a 1925 model, the only thing is, I am pretty sure that there were no Alternating-Current line powered sets in 1925. I'm pretty sure AC powered radios were an innovation of 1927-28. I am not sure of the model of the Kellogg RFL radio, but it might be the Model 520. Can anyone tell me a date as to when this radio was most likely produced? If so, please let me know.
Thank You

I have a Kellogg tube that looks like the one you describe. On the tube base, it says Kellogg type 401, AC tube. 2 pins on the top and 4 pins on the base.
401 tube data:
http://uv201.com/Tube_Pages/mccullough.htm
https://www.radiomuseum.org/tubes/tube_401.html

The Kellogg 'B' chassis using 6 - 401, 1 - 403 and a rectifier was manufactured in 1928, appears to be the only model I've found using that type tube..