Same Stamp But Different Stamp

What do I call these stamps.

If they weren't separated they'd be se-tenant! The stamps are part of the UK British Explorers series (SG #923-927) issued on April 18, 1973 as shown on this FDC that I found on-line:



[edit] Scott Catalog numbers are Great Britain 689-692.

Argentina

1971

definitive

Stamps of Guillemo Brown

Croatia

1991

Airmail definitive

1v.

Beginning in 1990, Ireland's seventh definitive series was printed by lithography by Irish Security Stamp Printing, Ltd. on unwatermarked paper. The black printing on these stamps is grayish, and the background colors fade in intensity, via halftone screening, from top to bottom.

Six values of the set were reprinted by Enschede. These stamps were also printed by lithography on unwatermarked paper. The black color and background colors on these stamps are more intense. Also, the halftone screen is finer, and it is set at a different angle on the Enschede printings, as shown on the right in the pics below.

Here are two Machin 2nd rate booklet stamps from 1990. The stamp on the left (S.G. #1511) is photogravure printed by Harrison. It is perforated 15 x 14. The stamp on the right (S.G. #1515) is offset lithography printing by Walsall. It is perforated 14.

The close-up pic shows the saw-tooth edges of the left frame edge and numerals which are characteristic of gravure printings. There are other details which make the stamps distinguishable. Note the somewhat pointed front of the breast on the Harrison printing.

The US 1998 Weathervane Rooster 1-cent make-up rate stamps were issued in two formats:
Left: 18mm high design with thin lettering, a white USA, and a black 1998 date, produced by Ashton Potter.
Right: 17mm high design with thick lettering, a pale blue USA, and a blue 1998 date, produced by Banknote Corporation of America.

Definitives from DDR

The first 1-cent Franklin and 2-cent Washington coil stamps (1908) were perforated either 12 horizontally or 12 vertically.

These Bulgaria 1961 mushroom stamps were issued with and without perforation.