Model2128Ga - That's a very nice A Grade; and you won't find many SAC guns with unmolested screws; a very nice find indeed. Interestingly, the serial number of your gun is very close to the serial number of the Grade A gun depicted in the 1902 and 1903 large SAC catalogs, as well as the 1904 pocket catalog, SN 25317. The SN of the D Grade gun depicted in the 1902 and 1903 SAC catalogs is 25307 (Grade C and D was not depicted in any pocket catalog I've seen); that gun still exists, and the Grade A and D guns in those catalogs are the only high-grade serial numbers legible. My SN research indicates that high-grade SAC guns have frames numbered in blocks, and I assume that is because of the manner in which frames were sent to the engraver.
CZ - The SAC trigger guard does indeed give the gun a unique look. The earliest Hollenbeck marked SAC guns had a more traditional shape; but SAC adopted the flattened guard bow feature after only a few hundred guns, and I don't recall seeing that feature on any original example with a 4-digit serial number. I theorize that the change may have been made to accommodate gloved fingers; but it could have been a feature adopted simply to give the SAC gun a unique/slightly different "look" than their competition.
Interesting note on the On/Off device is that, in the 1902 catalog, the only high-grade SAC gun (any grade gun) depiction featuring that device was the Grade D. That feature was noted in the other (and in the Grade D depiction also) as follows: "We also attach to this grade of gun, without extra charge, our new device (patent applied for) for instantly changing gun from an Automatic Ejector to a Non-Ejector". On all hammerless grades lower that Grade A, the On/Off device could be ordered for an additional $5 on guns ordered with the SAC auto-ejector option; but auto-ejectors were available as a standard feature on all Grade A guns from the time (1895-96?) the company began fitting auto ejectors to their guns.
