Frame types (Ir / IIr)
On a few fields of the fifth design we find the so-called frame type. It is easy to recognise — in the right part of the stamp the frame runs unbroken, whereas normally it is interrupted.
The unbroken frame is the result of a retouch of the printing plate and is designated IIr; the interrupted frame is type Ir. Type IIr occurs on just five stamp fields in all, on the values 10h, 75h and 500h.

Stamp fields
5 stamp fields in all. Hovering sharpens the thumbnail; clicking opens the specimen full-screen.
55/I
1/I
2/I
21/I
93/I