Well, as someone who got into revolvers early in life----back when they all had names--------and those names were used as the EXCLUSIVE means of identification (never mind each of those names also had a model number which was used pretty much solely by the factory and perhaps also by distributors---or so I'm told), I have come to truly despise the use of model numbers as the common means of identification.
Accordingly, this is going take awhile; 'cause I'm going to have to look up some of these model numbers.
While I'm doing that, consider your reaction if you didn't know beans from apple butter about these things; but were in the market for what I'll refer to as a combat handgun-----------and the store clerk offered you the choice of a S&W Model 19---or a Colt Python----or maybe even a S&W Combat Magnum. And consider your reaction if you were S&W's Marketing V. P.---and you found out about it. As for me, I was a Marketing V. P.----and such romantic names as Model # So&So would be BANNED from use, and those who took exception would be found hanging from a high rack!!
END OF RANT!!
A Model 18 is a .22 caliber Combat Masterpiece.
A Model 17 is a K-22 Masterpiece.
The most obvious difference between the two is barrel length---4" for the Combat Masterpiece, 6" for the K-22 Masterpiece. (although I'm thinking the K-22 Masterpiece can now be had with several different barrel lengths)----which, in my mind, serves to confuse the retail buyers----and confusing buyers is a sure-fire way to the poor house.
The Model 13 is a fixed sight 357 Magnum revolver, which I reckon is a cheap date for municipal treasurers to buy for their Police Departments------which deserve better!
A Model 14 is a K-38 Masterpiece (See K-22 Masterpiece, only chambered for .38 Special ammunition). It is arguably the finest centerfire target revolver ever made-----as is the K-22 Masterpiece in the rim fire category.
A word to the wise considering classic Bullseye competition (by whatever name it may now be known) is forget about revolvers and buy target grade autoloaders------which will simplify your life in the timed and rapid fire portions of the competition---assuming they still have timed and rapid fire---and haven't done away with them to even up the competition so the losers won't feel so bad.
Ralph Tremaine