Opinion:
I would suggest that hole, has not been "punched" intentionally, or by a folder punch.
From past experience, my thoughts would go along 2 routes.
1. The central embossed section has been die punched too deep, and the
punch has cut the paper to depth where the central portion has eventually fallen out.
or
2. Persons unknown have physically cut out the central section for unknown reasons
(I have seen this occur on Canadian KG5 stmaps IIRC)
A high def scan of the edges of the hole, may offer further insight.
