This issue has two different main stamp formats:

Unitrade BK194 pane of Scott 1621c folded and stapled as cover for booklet
Scott 1621c booklet pane of 16 stamps (Scott 1621a x 4) (Unitrade BK194)
Scott 1621a se-tenant block of 4 stamps (Scott 1618-1621)
Scott 1618-1621 4 different 45 cent stamps from booklet pane (Scott 1621c)

Scott 1621b $1.80 face souvenir sheet of 4 stamps (Unitrade 1618i-1621ii)
Unitrade 1618i-1621ii 4 different 45 cent stamps from souvenir sheet (1621b)
Single stamps (Unitrade 1618i-1621ii) from the souvenir sheet (Scott 1621b) have minor indentation tagging differences when compared to the single stamps (Scott 1618-1621) from the booklet pane (Scott 1621c).