~ Sieh dich ~
This is something like "Don't judge a book by its cover." on an etched stein probably by J. W. Remy ca. 1900. Sometimes the first line is seen with a variant phrase "Sicher dich'' which has the same meaning.
Sieh dich,
für Schaum ist kein Bier.
Be observant (careful),
because foam isn't beer.

This verse is also found on the stein below, marked with the Mettlach logo, form number 1745, size number "V" ( Roman number 5) and dated 1901. The size number "V" means it is the fifth size down from 1 liter and in this case 1/4 liter which is also marked near the upper handle attachment.
Translation: Roy De Selms/Les Hopper compilation
Photo credits: Unknown