There are hundreds or more alternate worlds in the GURPS Infinite Worlds multiverse. Most of GURPS settings can be easily adopted as part of the Infinite Worlds settings which includes Infinity Unlimited. Note that GURPS 4e (2004) is not entirely consistent on how it uses the "^" (superscience)...
Naturally this threat is open for everybody, who wants to post something to GURPS Infinite Worlds .
On Bismarck-1 (Q5, current year 1940), Bismarck
was killed attempting to suppress the 1848 revolts in
Berlin. North and South Germany eventually unified
into two separate states as Austrian influence in Germany
waned. Britain, North Germany, and France have
formed a Triple Alliance to contain the expansionism of
the radical Russian Republic, while the United States
enters the earliest stages of TL7 and begins to exert its
full economic power.
First of all, Bismarck-1 is a Q5-world, means its in the same Quantum sector like "Homeline", the Earth the AH-travelers come from. So its relatives easy to travel betweenboth Earth and Homeline propably discovered Bismarck--1 quite some time ago (propably 20-30years ago).
The naming is straightforward. The Homeliners come, see the differences, discover, that the "Great Man" died long ago and name this Earth after him.
Its actually quite sometime between the POD and the present, 92 years. A lot can happen in this time. I assuming the forming of the two german sates happend lot later then 1870. The text says Austrian influenced waned, so I think Austria was still exiistant as thiis happend, but already so weaakend, that it couldn´t stop Prussia from swalloing Norther Germany.