Question:

I am unfamiliar with this in mold stamped back mark. Is it Redwing? If it isn’t
Redwing, do you know who manufactured it? It is on the bottom of a 6 1/2″
H. X 5 1/2″ diameter wax seal canning crock with a 3 1/8″ diameter
mouth. Thank you in advance…

Answer:

Cary, RWSCo stands for “Red Wing Stoneware Company.  So yes it is Red Wing.  Your piece is a Red Wing Safety Valve jar.  Your jar normally came with a medal hardware that would snap the lid in place once the jar was filled with preserves or other garden canned items.  Al Kohlman