Opinion on 1888 Canadian quarter with missing digit

This one has been bothering me. It is missing the 1 in the date. There are fields of discolouration in the area and above, but no clear sign of grinding - and, if any, it appears circulated afterwards. Not a known error, it is probably then a grease pack error. Collected long before the Chinese fakes arrived. Your thoughts?

 Yes, a clogged die error. 

I've circled a shape that looks like a 1 rotated to the left, though not the shape of the 1's used at the time. But to be sure, could someone give it their opinion?