I forget what the silver dot signifies.
The service bulletin you are thinking of only pertains to Rev. L TIU models.
Service Bulletin 05-22-18a.pdf
As for the Service Bulletin, I'm personally not convinced it solves any problems. I believe Adrian is of the same mind, and he spent considerable time analyzing the failures of the TIU's. Adrian observed that the new "fix" described in the above service bulletin was getting slammed by transients at his location and the TVS parts were still failing.
I have designed a modification of a fix that Adrian made, it was pretty widely discussed in the DCS forum. Adrian did the primary field work on this, but his fix was bulky and complicated to install. This board was an attempt to provide the same protection in a much smaller footprint package with less connections. I truthfully haven't had the time to follow up and actually kit up parts and make this a real thing, but at some point I may get to it.
This module perches right on top of the 74ACT244 chips that are the one damaged by the voltage transients. This provides protection from high voltage spikes while not loading the DCS signal with the excessive capacitance of a TVS diode directly across the chip. The Schottky diodes isolate the large TVS stray capacitance from the DCS signal while still allowing clamping of any damaging voltage spike. Also, this module uses a TVS diode with three times the power rating of the "fix" that MTH is recommending.
I hope that answers some of your questions.
