Hi all ~ Since I emailed my initial inquiry, I've observed a few additional differences between my two A-250's (earlier machine is ser. no: SM-1429, later machine is ser. no. SM-13417):
1) The upper receptacle for the grille on the earlier A-250 is only 1/4" deep (vertically), compared to 1/2" depth on the later one. Both have 13/16" wide channels for the grill, to accommodate a full 3/4" thick grill frame with no tongue. 2) Serial number plate on the early one has a latest patent date of August 28, 1911; Serial number plate on the later one has a latest patent date of March 11, 1913. 3) The horn bumper mounted just inside the left edge of the grill opening has a 1/4" block spacer on the earlier machine and the later one does not have this spacer. 4) The fretwork of the grill on the earlier machine was 5/16" thick (based on two remnant bits), while it was actually slightly thicker (3/8") on the later machine. At a glance, the only real difference that stands out prominently is the user-adjustable semi-automatic stop lever. Does anyone know if this was the first type, and how late it was in use? I've copied a summary of other differences below. I would very much like to narrow down the date of manufacture of this machine. Thanks, Andy The turntable stop can be activated to manually start as well as stop by a single lever with a round knob. Also, the stop lever is not adjustable with the familiar lock-down screw under the turntable, and the "finger" on the lift post is a separate piece, mounted with a snug swivel, making it a user-adjustable stop (as opposed to a rigid finger). The other differences that I noticed during the cleaning are: 1) The keyhole trim is different from my later A-250, being nearly flush and fitted within the millwork of the keyholes, as opposed to being affixed to the surface only, with two small round-head gold pins through round upper and lower rings, as found on the later machine. 2) The veneer on the sides is a richer grain, and in one piece (my later A-250 has the side veneer in two sections). 3) The inside of the horn compartment has a high-class factory finish which is as smooth and shiny as the drawer fronts and inside of the door. 4) There are two pivoting oil hole covers in view (with the turntable installed), whereas the later machine has one. 5) The veneer is noticeably thicker (based on chips at the bottom of the back panel near the base of the machine).
