When I looked at the back of the chassis I seen two sets of figures, one on each of the "square cans". On the 5 tuber there was one ?455?--(maybe yo or kc. On the 6 tuber only one 455-no letters were visable. Are they the "if" cans? The tops of all 4 "cans" have 2 tiny screws down inside of each one. The 6 tuber does not have another "can", only just the two. Could there be another coil somewhere? You called it "pre-selector". Maybe I could pull the 6 tuber chassis & look underneath. I checked the 5 tuber. It has a 12SA7,12SK7,12SQ7,50L6 & a 35Z5 set of tubes. The 6 tuber has a 12SK7,12SA7,12SK7,12SQ7,35L6 & a 35Z5 set of tubes. I love taking things apart & putting them together again. My favorite is grinding out rivets & putting in screws & nuts so things can be repaired over & over again! Like JOE says on TV (2nd wind exercise) "why buy new when slightly used will do"?

: When I looked at the back of the chassis I seen two sets of figures, one on each of the "square cans". On the 5 tuber there was one ?455?--(maybe yo or kc. On the 6 tuber only one 455-no letters were visable. Are they the "if" cans? The tops of all 4 "cans" have 2 tiny screws down inside of each one. The 6 tuber does not have another "can", only just the two. Could there be another coil somewhere? You called it "pre-selector". Maybe I could pull the 6 tuber chassis & look underneath. I checked the 5 tuber. It has a 12SA7,12SK7,12SQ7,50L6 & a 35Z5 set of tubes. The 6 tuber has a 12SK7,12SA7,12SK7,12SQ7,35L6 & a 35Z5 set of tubes. I love taking things apart & putting them together again. My favorite is grinding out rivets & putting in screws & nuts so things can be repaired over & over again! Like JOE says on TV (2nd wind exercise) "why buy new when slightly used will do"?
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You need to go to E-bay or another computer site where one searches for items, bibs, and buys them, and look for an RCA Receiving Tube Manual (any), and / or Amateur Radio Handbook (ARRL - Amateur Radio Relay League) pre 1955, and buy them. These have good information on how the various parts of radios work, what they look like, etc. That way you will not be flying blind. Also be aware that tube radios have high voltages inside that are dangerous, and in many cases, one side of the line is connected to the chassis, which can be dangerous. ESPECIALLY with the tube lineup you describe. Ed M