Hi, I need some help in identifying an unknown Silver Stamp please.
It is the only Stamp on the rear of a Victorian Silver Cross Brooch… Interestingly I have also found the same Stamp on the reverse of a Victorian Costume Jewellery Brooch as well, so I am assuming that this is either a Makers Mark or a Location Mark?
Any help would be greatly appreciated, I have included a picture of the Silver Brooch and Stamp, and also a picture of the Costume Brooch and Stamp for comparison.
These marks are design registration marks. Normally the large letter R would be followed by a superscript “d”, standing for Registered, but in this case it seems that the makers have dispensed with that detail. The mark defines the material used in the design and the registration date so it gives an earliest possible date of production, but not the actual date. A guide to reading these marks can be found here (and in other places on the net).
For your silver-coloured brooch the mark is too rubbed to discern any details, but for the brassy-coloured one we can say that it is made of metal and that the design was registered on 27th January 1870.
Phil
Fantastic… Thanks Phil, much appreciated! 
