I notice the example you show is 1899 - how does that fit in with mine
beating the EKU by 2 years?
Yes, indeedy !
Yours beat the EKU, but it only captured the record for about 10 minutes,
then Googling found the earlier postmarks.
10 minutes of fame
Marketing that stamp would be a real interesting experience,
Unique, but finding the right customer, difficult.
I'd keep it, if it were mine.
One may ponder how it happened, maybe a postage due was affixed close by, maybe an enthusiastic clerk, cancelling a missed stamp.