Old Tokoname Bonsai Pot

This old Tokoname bonsai pot from Marushi Shigeharu, by Mr. Sawada Shigeharu has the usual pot stamp, pictured here in the centre.

The mark on the right, however, has not been identified.  It is the only pot of this type, that I have found, that has this additional mark.

If anyone has a pot like this with the second mark please let me know.  Better still, if you know it's meaning it would be great to find out.!!