The possibility has always existed that the passenger manifest believed to list our Gustave MEYER was not the correct document. Even after narrowing down the time frame to between 1872 and 1874 -- based on census records and family history -- there are a handful of passenger lists with boys approximately 16 years old and named Gustave MEYER on their way from Germany to America. (Searching for the name alone in that era yields even more matches.) The October 1, 1873 passenger list of the S.S. Holsatia, for reasons I now can't remember (red flag!), seemed like the best fit years ago.
Ordering the microfilm of Hamburg emigration lists to verify Gustave MEYER's supposed passenger list was not a priority, but it should have been. After recently seeing that the boy by this name on the S.S. Holsatia was from Magdeburg (Sachsen-Anhalt), I realized our Gustave, born in Evinghausen (Hannover), would have to go back on the immigration "to do" list. He's not alone. I've yet to find Gustave's brother Louis on a passenger list in the 1880s.
Obviously, individuals who traveled alone are sometimes harder to identify on passenger lists, especially when their surname is anything but unique. I knew that, but I suppose I was hoping to have initially found the right list.
It looks like the best bet for figuring out which ships the MEYER brothers came to America on is to order the alphabetical indexes for the Hamburg emigration lists. Even doing that will be somewhat of a crapshoot, though, since it's not certain that Hamburg was in fact the port of departure. There is a good chance that Gustave and Louis left from Bremen. In fact, a quick check of Germans to America and Ancestry's database shows more possible matches on ships from Bremen than Hamburg.
The lesson here is that if your ancestors left from Hamburg, by all means order the microfilm of the Hamburg emigration list to verify the arrival passenger list. This may not be necessary if the family name was rare or the traveling party was large and identifiable, but for a few bucks it's worth the confirmation.