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?

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.