Gorham (NH) mile marker

I have a question (2, actually) about a mile marker by the former Grand Trunk depot in Gorham, NH. One side says "B 6", which I assume means "6 miles to Berlin, NH", while the other side says "C 149".

1. Why are they measuring the distance from Berlin? Looks like a minor waypoint to me.

2. What does "C 149" refer to? As best I can figure looking at my maps, the former GT line doesn't have anywhere close to 149 miles extending east of Gorham.

Thanks.

At one time, the White Mountains Division of the B&M had a through route between Berlin and Concord, N.H. via Littleton, Woodsville and Plymouth. The line was a branch of the old Boston, Concord and Montreal Railroad. Its main line ran from Concord to Woodsville. Most of it is now abandoned. The B,C&M was leased by the Boston & Lowell in 1884 and was subsequently merged into the Boston & Maine in 1887. Mile markers, had a "C" on it for southward moves and "B" on it for northward moves.

That then begs the question of why a B&M milemarker is on the GT line through Gorham.

Wasn't Berlin the north end of the "Conn River Main"? So it would have B on one side of the milepost and a WRJ or S (or SP?) (for Springfield) on the other side. Presently, the B&M mileposts still exist along the Brattleboro-Windsor (VT) section of the former Conn River Line but are painted over, and a modern metal milepost installed next to it, depicting mileage from New London CT (former B&M line taken over by CV/NECR c 1988 due to an Amtrak dispute).

Regardless, the fact that a B&M/MEC style milepost was in Gorham is probably the same reason why a B&M engine is on display alongside a GT line: because there's a "museum" of sorts there with various railroad equipment on display. Said milepost was most likely acquired by/installed by the Gorham Historical Society. While it may be a railroad artifact, it's not in a historically-accurate location. The average person visiting the museum isn't going to know the difference. However, we would all spot the inaccuracy right away!

My copy of Richard Carpenter's A Railroad Atlas of the United States in 1946 Vol. 2 and UNH's Historic USGS map collection show the B&M Gorham station 2 miles NW of the GT station. The mileages are correct for Concord and Berlin. It is marked from Concord because the line built as a continuation of the Boston, Concord & Montreal via Plymouth and Woodsville.