You've probably already seen this picture of the 15GP22 and a never-marketed 19GP22.
There's yet another picture from a 1954 magazine article lead of a Dumont 19-inch experimental "Chroma-Sync" tricolor picture tube. [Regrettably, the editorial direction of the article had nothing to do with the subject of the illustration -- a sure indication of less than optimal editorial skills at work. (Check the edition of "Basic Electronics" that author Bernard Grob last contributed to. Somehow, clearly beyond control of the author, the work got peppered with splashy 4-color illustrations that provide no worthwhile -- even misleading -- value for a serious reader.)]
The next sound you hear will be Pete stepping off his soap box.
However, the good we derive from this lack of editorial continuity is this picture of a hitherto little known experimental 19-inch tricolor CRT from Dumont. This is clearly not of early RCA design because there is no internal decorative mask. Here, the phosphor dot trios were deposited directly on the inside of a round face plate, as CBS always did and RCA began by the end of 1954 with its 21AXP22.