Edit: It was built in 1950 as B&M 1174, rebuilt in 1957 as B&M 1274.

It had last been used by the University of Minnesota, who donated it to the museum. The museum then had to come up with the funds to move it. This group is employing the semi-truck wrecker approach rather than renting cranes, which could possibly save groups a lot of money. Here it is being placed on its trucks today: https://www.facebook.com/gopherstaterailwaymuseum/

I have been following this engine from long distance now for over ten years. Although it has been posted that the loco is ex-B&M 1274, the evidence now stands that only the CAB is of B&M origin. There are several reasons for this confusion.
When I was first introduced to the image showing the shadow of the B&M Minuteman herald on the cab side I was tasked to help identify it. The first plain to see feature was that the cab windows were the later rounded corner rubber gasketed style. Only B&M S-3 locos had this feature. So the first thought was the unit MIGHT be the 1274 that had been B&M 1174 rebuilt by Alco to S-4 status after a roundhouse fire.
Sadly, the photos I had to work with at the time were relatively small with poor detailing due to the nature of them of the day. So we left it as it MIGHT be the 1274. Now that the units has surfaced with better images, I can clearly see details that say the main part of the loco is not B&M.
1. The number indicators are too small. The B&M used the oversized option (that few roads used) on their S-3's and 4's.
2. The engineer's side of the hood clearly shows to me now and has the short door by the air filters. The B&M 1174/1274 would not have this.
3. The battery box is the larger S-4 style while the 1274 would have still had the smaller S-3 style.
4. Still to be confirmed, it is a simple matter to measure the length of the frame over the pilot faces and see if it is 40'-6" or 41'-6" and this is what separates turbo from non-turbo units out of Alco. S-2 and S-4 had the longer frames. B&M 1174/1274 has the shorter frame and Alco had to shoehorn the extra goods into that smaller space to make it a turbo unit.
My best guess is that the cab is actually one of the many S-3 units that went to Naporano in Newark, NJ for scrapping. Naporano may have done the cab swap and saved the loco or they may have supplied the cab to rescue that loco and somebody else did the swap.
Time will tell.....