I have a '65 RCA and the agitator is definitely not a "snap-on" unit. So I think the eBay seller may be incorrect in saying this will fit "GE/Hotpoint/RCA".
GE made RCA washers (very THINLY rebadged GE Filter-Flo's)in the late '80's early '90's. Virtually identical to GE/Hotpoints in every way. They had a snazzy dark grey/red backsplash.
from 1956 to 1967...that is how RCA and Whirlpool were connected.... prior to that RCA owned (or maybe was just afilliated with) the Estate Stove company (which I believe Whirlpool bought circa 1955) and also manufactured room A/C units in the early and mid 1950's
PAT COFFEY
In 1986 GE bought RCA to get its hands on NBC which was owned by RCA in 1987 GE sold the electronics divison of RCA to Thompson Huston Corp. who then turned around and made electronics with both the RCA and GE names on them. PAT COFFEY