It looks like the potter’s wheel mark of Marzi & Remy. Can you make out the initials M and R on each side of the vertical line? I couldn’t find mold 699 in any catalog for them. The old catalog does show a pouring pitcher with that number.
You might be able to see it better on the stein itself. The Old Manufacturing Catalogs (see Reading section) shows both mold 669 and 696, but the photos are not very good. You might need to rotate your stein to match it to one of the two molds, both of which are poring pitchers. I am pretty sure you have one of those two Marzi & Remy steins.