Hi Jeff, the Westinghouse Air Brake packing cups in the 68500 series, like shown in your picture above, were available from normal WABCO parts sources. Most sizes were a stock item until a couple of years ago when they went to Made To Order (MTO). They were made by the Wabtec Rubber Products, 269 Donohoe Road, Greenburg, PA, 724-838-1317. I have had needed information about the status of WABCO rubber products in the past and had success calling the rubber plant directly.
Originally Westinghouse Air Brake used leather cups and the 68500 series rubber cups were a direct replacement. However, the leather cups were used with an expander ring that is not used with the rubber cups. If you look at the iron piston you should see a grove in it where the expander ring was located. As I recall the ring was about 10 gauge spring steel wire rolled to a ring with just enough gap at the ends to get it installed. CW Marsh is an excellent source for leather cups, but you will need to come up with an expander. The advantage of leather is that it has an almost unlimited shelf life. As I recall the rubber cups have a 5 year shelf life. Both cups would be used with the AAR brake cylinder lubricate. Keeping the rubber cups in a zip lock bag with a little Armoral added will extend their shelf life.
Please let us know what you learn. Keeping track of suppliers of railway parts to museums is a never ending challenge.
Thanks,
David Johnston
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