Finding myself with a bit of spare time over the past month, I dug a little deeper into the "to-do" pile. First off was replacing the display in a DC508 counter:
tekdc508front.jpg
The OEM readout uses three Siemens DL-883A 3-digit displays - which have long since become unobtanium. One of the guys on the Yahoo Tek500 Forum made a limited run, aftermarket readout board using discrete single-digit SMD LEDs which fits both the DC508 and DC508A counters.
I HIGHLY recommend this board if you have a '508 series counter. Installation took a couple hours, mostly due to the fact that my big fingers are a little challenged in small spaces - and there isn't a lot of room to work with in those smallish modules.
FWIW, if one can find a junker DC-503 (not the -'A' variant) and one has access to an ESD-safe vacuum desoldering station, the readout board may be removed and the center display can subsequently be desoldered and used to fix your '508.
As it stands, I now have a pair of readouts with which to fix my '503s should they ever go bad.