Not as common as the 38, but there are quite a few of them around. The so called first issue Cobra was made from 1950-72, and was produced in 22, 32, and 38 caliber. I believe the 22, and the 32, were dropped from the later versions of the Cobra. I don't know if any exact numbers are available, but I would guess most were in 38, and the least numbers were in 22. It's tougher to find these in top condition because of the alloy frame finish being so easily damaged.
moosedog; I had a 4" .32 Cobra,made in 1965,next to last year of the full grip frame.
I agree with ohiobuckeye about the years being offered,as with the change to the shrouded ejector,72',it was only .38 special(but who knows about "special orders).
The rarest caliber Cobra,and Detective Special,is in .38 New Police,Colts name for the .38 S&W. This was listed in the catalogs,but a special order-and rare.
One of my 3 remaining D frames,is a 1971 Cobra 3" .22,that I bought NIB in 1990. It is NOT unfired NOW! Served my daughter while she was in graduate school in Boston;never had to use it thankfully,but had to "show it" to a "rag head",who was slapping his girl friend around; one of my daughter's roomates! Very accurate & smooth,still looks new,but the lack of adjustable sights,hurt it sales vs. the S&W Kit Guns.
Rarest Cobra,I know of,are the 5", square butts, .38 Specials,made for Venezuela's military in the early -mid 50's. Some of the "survivors" were reimported back to the states by Sarco,I think, about 10-15 yrs. ago. They were in real rough shape,especially,as ohiobuckeye said,the alloy frames. Very dedicated collector ordered one,through our local gunshop(can't recall the price-but it was NOT low cost "surplus". Anyway,happened to be in the shop,when UPS delivered it;pretty rough shape,so I didn't order one!