The following pictures show the marks used by WMF on metalware (pics A through E and 1 to 7) and glass and ceramics  from the 1880's to the present:

((D) from 1909 on; (E) from June 1910 usually a very small mark; (1) from 1907 on printed material; (2) from 1907 on Orivit items together with Orivit design nrs.; (3) on items originally designed by Orivit

(4) 1925 - 1935, after 1935 the upper "bow" is without lines; (5) from 1965; (6) 1938 - 1948 on silverplated ironware with copper or brass layer; (7) 1939 - 1945 on silverplated zinc items.

Additional markings:
MB    -    partly brass/Britannia-metal
B       -    Britannia-metal
O       -    extra thick silver coating
I/O     -    regular silver coating
OX    -    Oxidized.
as      -    antique silver finish
zg      -    fancy gilt
gg     -    entirely gilt
go     -    parcel gilt
bg     --    gilt base
ig      -    gilt interior
M      -    brass
N,  NS - ;    nickel-silver
brass, copper   - Export Marken f|r Messing bzw. Kupfer           export marks
ep    -    electro plated

Also there was from around 1925 to the 1950's a significant production of art-glass (Myra and Ikora) and art-pottery, the last only produced from 1935 - 1949. There the following marks can be found imprinted, engraved or as sticker:

Source: WMF. Glas-Keramik-Metall 1925-1950 (Exhibition catalogue)

(c) G|nter Staffa 1998-2001