Ken, the Hunter Arms Co. for anything above a No.3 would be special ordered, unless it has ejectors or a Hunter One Trigger. In some of the early catalogs on the last page was an order form that you filled out stating what you wanted as to LOP, DAH, DAC. If you filled in the length of pull and ordered the HOT they automatically made the stock to your length whether the trigger was in the middle or rear position. The also stated if you wanted a particular pattern at the yardage you preferred they asked what powder you were using and the shot size. On the top floor they would pattern it to your specifications and send you the results.
Your are very fortunate to have the Glahn's name on it. SC means scribed (signed).
The Spangler brothers first worked for L.C. in Syracuse and later went to Fulton when Syracuse was sold. Glahn and his 3 sons also went to Fulton. Not much info on how long the Spangler Bros. stayed on. In his obituary, Joseph Glahn went to Fulton in 1893 as head engraver and died in 1902.
Here is the conundrum, your gun according to the Year of Manufacture states 1891. Who is right? Researching is fun until things like this happen.

Also does your A2 have the stepped lock plates? That is the first style and there were 4 different styles. In my opinion the first style A2 was the nicest of any of the Fulton L.C. Smith's.