I'm trying to attach lineages (type, builder, and year built) to the Ann Arbor boxcars listed in the April 1957 ORER. I've found something for all except for:

XM, 250 to 299, 40'6" IL, 10'6"IH, 3892 cu ft, 100000lb, 6' door

This series does not appear in the Jan 1953 ORER, and is in the April 1958 and April 1959 ORERs, which leads me to believe it's a mid-50s boxcar, but I can't find the series in any of the standard roster sources (including a search of the past messages for this group).

Thanks in advance for any information,

Charles Hostetler
Goshen, IN