On Nov 15, 6:55*pm, martin wrote:
I got a bit of a surprise this morning when an Oyster Refund
Confirmation popped up in my inbox. *Looking at my journey history, it
appears that there's an OSI between Sydenham and Crystal Palace
stations, with a time limit of at least 25 minutes.

This one doesn't seem to be on any of the lists that I can find. I
wonder how many more secret OSIs there are out there?

May have been a temporary setting. Were there any planned service
closures that day? If so, Sydenham may have been set to interchange
with any station on the network.