~
From this
thread.
FIRST TWO DIGITS
39: 9mm
59: 9mm
69: 9mm
10: 10mm
40: 40S&W
45: 45 ACP
35: .357 TSW
THIRD DIGIT
0: standard model
1: compact
2: standard with decocker
3: compact with decocker
4: standard with DAO
6: nonstandard barrel length
7: nonstandard barrel length with decocker
8: nonstandard barrel length with DAO
FOURTH DIGIT
3: aluminum frame with SS slide
4: aluminum frame with carbon steel slide
5: carbon steel frame and slide
6: SS frame and slide
7: SS frame and carbon steel slide
*** Source
SCSW, 3rd Ed.
There never was a 3919, but a 3 can look like a 9 under the right conditions. There was a revolver thread about a year ago, where the OP insisted that he had looked at a S&W chambered in ".36 Special" caliber. A closer re look showed that he had mistaken the 8 for a 6.
As to the ad in GunsAmerica, I'd suspect a typo as well.
There are enough 3rd generation experts (I'm not one) on this forum that if it existed someone would have seen one and probably own it was well.