USA 2c red pre-stamped envelope
Uprated 1922 for registration to Berlin, Germany with 3c (straight-edge) & 10c stamps pen-cancelled
Corner Card: (architects)
Cervin and Horn, 310 Safety Bldg., Rock Island, ILL.
No place-name cancellations on the front, but an inverted registration stamp.
Cancellations on reverse:
New York USA / Foreign 5-4-
and very faint violet marks apparently dated MAY 7 1922, which would seem to rule out Rock Island ILL.
Interesting oval violet Berlin postal mark.