I did some more looking and all the barrel flats where I can see the area down into the low 149xxx range have the J.G. in oval and &. Serial 148762 has W.K in the oval and the & --
148762 03 V in circle barrel steel, W.K. in oval and &.jpg
The highest serial number I've recorded with the & is 180703. The J.G. in an oval continues into the 219xxx range as the PARKER BROS. OVERLOAD PROVED stamp came into use.
The symbol really looks like a "Concern for POWs" or "Breast Cancer Awareness" ribbon and a small c.