I was recently at a friends place and he had a 5 round clip that had come out of a box labelled .256 Fraser. All 5 cartridges were loaded the same and 3 of them had the usual Greek military headstamps of the 6.4x54 Mannlicher. The other 2 cartridges had an Eley headstamp I hadnt seen previously, the one in the photo has a primer ring crimp but the other didnt.
Is this headstamp unusual? What do the “SR” and “E” stand for?