[Ron Ramirez]

Then you are going to want a Model 90 with a single 47 output, early production of the middle version chassis, above serial number 237000 but not too much above that serial number as Philco soon switched to bakelite escutcheons after the switch to the chassis with AVC and single 47 output tube.

A look at a graph, showing serial numbers versus production months, is revealing:
http://www.philcorepairbench.com/graphs.htm
(scroll about 2/3 of the way down the page to see this chart, showing model 50, 70 and 90 serial number data)

Philco did not start using code numbers until the June 1932 models were released.