Like many cyclists, I rotate a set of chains (two chains every 1000 km in my case) to minimise gear wear and have an opportunity to do a deep chain wash every now and then. When the time comes, I replace both chains and the cassette, and the chainrings every second time.
This pattern results in a good lifetime for the transmission, but it means each chain is removed and placed back many times.
The chains I use (HG93) don't have a special connector link.
For safety, it's not good to extract the same regular pin more than once.
So what is the best way to mark the pins that were once extracted?
A very close inspection can identify them by some flashing and scratches, but this is slow and tedious, and never reliable. Sometimes I mark the extracted pins (or whole links) with the etch primer (other paints may not last through the use and wash cycles), but I don't always have it at hand.
What other simple methods do you use or know?