This can be a little confusing. Any one can see there
are clearly two lines at the end of the ribbon for types I, Ia and II, and three
at the end of Type III. Technically the second line, and the second and
third lines in the type III, are lines of shading. One of the easiest ways
for quick identification is to look for a "V" or a "IV"
at the end of the left ribbon. Only the type III has the "IV",
formed by 3 lines, or 2 lines of shading, as it were.
If you still haven't narrowed it down to a Type I, Ia or II
Vs a Type III, take a look at the right ribbon. In particular, the extra
line of shading in the Type III stamp is sometimes hard to see. It is always
a good idea to check the right ribbon for verification.