Slight correction. It is perhaps more accurately the PA/RF deck part of the TDH transmitter, the big brother to the TDO. Might be also known as 51D but I have no info on that model number. My source is Navships 900,798. 1944 vintage, 3KW output, 2-18.1KC, pair of 750TL output tubes. COL-52343. Neat rig. Don W5OR