For doors built around the same era as most of Breckenridge's commercial stock, the parts that fail most often are torsion springs sized for the lighter track systems common in 1960s construction, steel rollers to replace the ones that have worn oval instead of round, and lift cables that have started to fray from age rather than misuse. We carry these in the sizes that fit that older hardware, not just the sizes that fit what's being installed new today - that distinction matters on a door this old, because a modern spring on old track can bind.
We also stock weatherseal and bottom astragal material suited to a severe cold climate, since the freeze-thaw cycling this area sees is what chews through rubber seals faster than sun does. If your building's door has already been upgraded to a newer insulated panel, we carry parts for that too - but the calls we get most from Breckenridge are still on the original-era steel sectional doors, and that's what we stock deepest for.