To complete the story, the target hammers were first introduced
in very late 1949/early 1950. At that time, the hammer design was
the so-called fish-hook style, in which the hammer tang (spar) is turned
upwards. In the factory records, a very early target-hammer
is referred to as a "low-spar" hammer. I imagine this is because,
relative to the upturned-spar standard hammer, the spar on the
target hammer is very low !

Regards, Mike Priwer