Welcome to the Forum. Those are uncommon stocks to run across. They only appeared on one model that I can find and were only produced for less than 3 years.
The earliest stocks made of black hard rubber were for the 32 Single Action and the 38 Single Action revolver models. The block letter style was standard until Gustave Young designed the now familiar intertwined S&W logo. Sometime during the 1879 production runs the standard round intertwined logo at the top of the stocks were used on all models.
The rubber stocks you show started with the 38 Single Action, 1st Model revolver in 1876. The 38 SA had three designs for the top round section. The first two were S&W in block letters that ran until the introduction of the intertwined S&W logo. Change-over was done in 1879 and all 38 SA, 2nd Models after that date had the Young design logo that became standard on all revolvers.
The added image was the very first block letter style stock and yours is the second block letter style.
__________________
Gary
SWCA 2515
Last edited by glowe; 05-16-2020 at 09:21 AM.
Reason: added image