I didnt see that pre fix anywhere in the book. Can someone cite the page number?
I assume you are talking the Standard Catalog of Smith and Wesson by Supica and Nahas? I have the 3rd edition open in front of me. On page 400, under All Other Revolver Models, for January of 1988 the listing of prefixes is AYE-AYM. For July of 1988 the listing is BBF. That leads me to assume that BAE occurred sometime after AYM and before BBF. All caveats regarding assumptions hold true. Plus, note the disclaimer at the top of the page that SN start dates are approximate, and 'not all serial prefix letters were used to completion.'
Yup, according to SCSW the Model 36 no dash was made up until 1988 despite numerous engineering changes, including omitting the pinned barrel.
Anyway, S&W said frame milling for the hammer mounted firing pin required a special dedicated machine, that was expensive, and it is now gone. It is not coming back. I always "felt" better having a pinned barrel, never had a barrel unscrew, but having a pin there reassured me that it was not going to unscrew as long as the pin was in place.
They gave you an incomplete answer. In the old days, before CNC, many operations at S&W were performed on machinery dedicated to performing one specific task. Milling the slot in the hammer for the hammer mounted firing pin was probably done that way. One guy would have fired up that machine and milled dozens of hammers in one sitting. Plus the hammer would then have to be drilled for the rivet that held the firing pin in place. After all that was done, the hammer had to be heat treated for the classic S&W Case Hardening. Then it all had to be assembled.
Milling the slot in the frame for the firing pin to pass through may also have been a separate operation.
But what they didn't tell you is it is just CHEAPER to produce hammers that don't have firing pins in them. Hammers today are made by the Metal Injection Molding (MIM) process. Part of the cost savings with MIM parts is they are designed to emerge from the process as finished parts, without any further machining operations necessary. So it is simply CHEAPER for S&W to make MIM hammers today, that are completely finished, without needing further machining and assembly to pop a firing pin in place. Adding the frame mounted firing pin is also CHEAPER.
Here is a photo of the firing pin assembly removed from a Model 617-6. All that had to happen to the frame was drill a stepped hole for the firing pin and spring to sit in, and a cross hole for a retaining pin to secure the firing pin in place. The retaining pin is held in place when the side plate is screwed in place. This is called 'driving the cost' out of manufacturing. Bottom line is, S&W saves money producing revolvers this way.
P.S. I agree that probably very little energy is lost smacking a separate firing pin. Springs are very carefully specified. The return spring for the firing pin and the associated friction probably does not eat up much of the mainspring's energy.