Built date

BLT means built. The stencil is a month and a year, sometimes with the builder's initials beside it. It says when that carbody was constructed. It is painted on the car by the railroad or the builder. It is not a lookup into a private equipment register, and a website should not pretend an official build record is hiding behind the letters.

Keep the built date separate from the weighing dates next to it. NEW, when it appears, is the date the car was weighed new. A car finished at the end of one month and weighed at the start of the next can show two different dates, and both are honest. A reweigh date is later still. It says when the light weight was checked, not when the car was born.

Rebuilt cars may carry a rebuilt date as well as, or instead of, the original built date. A new stencil after a wreck repair or a stretch job is telling you about that work. If both dates survive, the earlier one is the birth and the later one is the rebuild. If only one date survives, don't invent the other.

For modelers, the built date is the start of a research trail: which production batch, which builder, which details were current that year. The stencil itself is only the date and, sometimes, who built it. The rest is prototype research, not something the letters encode.