Didn't find any off-the-shelf implementations in .NET so I gave up for the time being.
I might just end up adding a checksum to the ticket# and then computing all possible permutations that still meet the checksum, and verify each match against the database of open tickets. Takes less space anyway.
Back at my earlier workplace we used EAN-13s as product serial numbers. Generally in customer service we used the last 5 digits, with the leading ones being implied by product model.
"Has there been any progress on sausage-biscuit-club?"