There were several changes made to the 2nd Model and the pins were only one of them, as there were 4 changes made. They are found on page 88 of Neal/Jinks book. Don't forget that just because an engineering change was made on a certain date, those changed did not roll off the line the next day. Every model change is, at best, approximate since the factory was already in the process of assembling hundreds to thousands guns. There were also lots of parts made and they were used until those old parts were used. It is reasonable that new changes were not all applied for some time after the change order was issued.
The serial number ranges for various models and changes are the best estimates and observations available at the time the book was written, but I still believe it is just best to use those published serial numbers when identifying model changes. 33,501 was the official start of the 2nd Change, but the book states that no records were available to document the starting date of this model. What I believe of more interest is the statement made that Target sights were available on square butt models only??
BTW, I have 34793 and it shipped in 1908.
