EDIT Nov. 8, 2014:
Received an email from caboose9 apprising me that this caboose, when restored, became a fantasy caboose, painted with a number that never existed in the Milwaukee Road's inventory. Apparently the highest number used by the Milwaukee Road was 992301, or 992302, depending on who you read. The caboose was originally a Great Northern unit, built in 1967, then became the property of the Burlington Northern - #10066. So, it appears that, though it wears Milwaukee Road colours, this never was one of theirs. The paragraph below is from a comment at
Deviant Art.
Milwaukee Road caboose 992303 on display at Bonner, MT May 25, 2009. This caboose actually was never a MILW caboose. It is ex-BN Caboose 10066, nee-GN X146. It has been painted as MILW 992303, which is one number higher than the highest number of any MILW caboose that actually existed.
In a new park recreated as part of the Milltown Super Fund clean-up, this caboose has been restored and looks brand new. One could say that this caboose is either at Bonner or at Milltown. We're going to say Milltown, as it's closer than Bonner proper. This is a wide vision AAR Type M930 caboose. It was built in August of 1975 and rebuilt in May of 1999.