PhysDoc called my attention to this item (
http://www.gunauction.com/buy/12565717#) offered for sale, which would seem to contradict my analysis of the situation. The rifle in question, evidently a low numbered Springfield 1903, is equipped with a port side receiver sight, which seems to be an ordinary starboard side sight which has somehow been converted. It does not appear to be a Lyman, but could be, I suppose, a Pacific. Why someone would go to all the trouble to mount a sight this way is beyond me. Maybe it was done on a bet.
I am familiar with the sight bases which allow various kinds of target receiver sights to be mounted on the left side of a
Springfield receiver, but as mentioned above, they are not compatible with a top scope mount, so I did not consider them.