[old_tv_nut]

CBS produced 19 inch outside diameter round color tubes, used in Westinghouse and Motorola sets as well. Motorola later went to 21 inch O.D. tubes from RCA.

RCA never produced 19 inch tubes. Both the metal shell 21AXP22 and the later all glass round tubes were 21 inch O.D.

The 21AX is subject to leakage problems. The one I originally had in my CTC-5 had a leak at a very small ding in the weld between the two metal pieces that join the face assembly to the bell, as verified by the first tests with the helium leak detector at ETF.
So, yes, if yours is good, be careful with it. If it is good, there is probably no reason to remove and handle it.

"Don't tell anyone if you replace the 21AX with all-glass" is stupid nonsense. Of course you would reveal this. Why would you care what someone else thinks about your decision to get a working set? It is a well known workaround to get a working set, and not revealing it in order to make a sale would be fraud.

Regarding rarity, the Super chassis is least rare for that year. There are quite a few parts sets still in existence (unfortunately, most with burned out DC convergence pots). Your DeLuxe is rarer and more desirable.