Thanks to the painters Saturday (September 17th, 2010)!
The caboose is most likely DM&IR 187. the D&IR had a few of these long (for that time period) cabooses built in 1887. At that time they were longer than the standard 4-wheel caboose being used on the railroad. Their orginal numbers would have been D&IR 87 and 89. After the merger of the D&IR and DM&N into the DM&IR in 1927 they were renumbered by placing a one in front of their number - eg #87 became #187, etc. At that time they were give class number K-3. D&IR did not use class numbers for their freight equipment, but since the DM&N did and they were running the show, they were provided class numbers. At some time (I think in the 1940's) the DM&IR changed their reporting marks (the letters used on their freight cars to identify the railroad) from DM&IR to DMIR.
The Missabe Railroad Historical Society has a web page where they list the DM&IR cabooses. http://www.missabe.com/caboose.html
They list K-3 cabooses 181, 184, 185, 187, 188 and 189. They have photos of 184, 187 and 189.
The photos show a small window on the end shown on the left of the photos of 184 and 189, but not on 187. There is not such a window on the caboose at Pine River. So based on the limited photos above, I would guess it may be caboose 187.
#184 was retired in 1947. The caboose you have was in use as late as 1960.
This is just a first guess. I will collect more information on this and get back to you later.
Please note the following colors off the top of my head with the approximate times used:
When built brick red - very dark red with gold leaf lettering
1920's mineral red with white lettering
1937 yellow with black lettering. In the 1950's lettering changed to vermillion on some equipment.
The caboose was repainted in September 2010 as part of the Valspar Grant for the paint. We had volunteers help prep and then paint the caboose. E-mail us your name and a contact phone number if interested in helping prep and finish this task. volunteers please e-mail - firstname.lastname@example.org and let us know your availability. We hope to eventually refurbish the interior to its original condition that served as the conductor's office and crew quarters. A large donation would be required to make this happen.
We have removed the orange fencing from the corners and replaced it with a small chain supporting a 'Keep Off Caboose' Sign. Thanks to Steve and Margo for handling this task.