Richard Hendrickson wrote:
"Paul, brakes were serviced more or less annually, like truck journal repacking, and the railroad, location, and date were stenciled on the reservoir or reservoir mounting."
"AB" brakes were required to be serviced every 36 months under the provisions of Interchange Rule 60. That service interval was a standard from 1934 until extended to 48 months by supplement to the 1958 Interchange Rules. "K" brake systems were required to be serviced every 15 months. I would have to look up the exact date that the service increment was extended to 15 months, but early on the interval for "K" brakes was every 12 months. The 15 month interval was in effect from (at least) the early 1930's into 1953. All references to "K" brakes were taken out of the Interchange Rules, effective January 1, 1960.
Prior to servicing the brake system the stenciled data applied when cars were new, or after the last service date, was recorded by the current servicing railroad for use in billing the owning railroad. Once cleaned, oiled and tested; all old stenciling was to be scraped away, painted over, and new stencils were to be applied as such; railroad shop initials, date (m-d-yr) and the servicing railroad's reporting marks.
Shop initials and the date was on the left side of the "AB" combined reservoir and the RR reporting marks were on the right. The shop initials and date were stacked over the RR reporting marks if placed on the end of the reservoir, they were stacked in the same manner on the smaller air reservoir of "K" brakes.
This was standard practice from the introduction of the "AB" brake system thru 1959. Stencils for brake components were 1" in height until 1938 when they were changed to 1-1/2" in height.
Any brake application in which the reservoir was obscured by deep side sills generally had the COTS information stenciled on the side of the car where the reservoir was mounted and placed as closely to the air release rod as possible. It was also permitted to stencil the information on the center sill of tank cars as spillage of commodities often obscured the stenciling unless protected by cover shields.