Old Sheffield Tray? Possible new Mappin mark?

[Shofner303]

I picked up this nice tray today and ran into a dead end while doing some research. I first assumed it was solid silver after a delicate acid test showed positive. However, after trying to identify the hallmarks I found myself learning about the "Old Sheffield" style of platting which is what I am assuming this tray might be. I was wondering if any of you experts could help me solidify the identity of this piece as I can not find its exact hallmarks cataloged anywhere.

The tray is 12" (31cm) in diameter with the only hallmarks are on the front inside edge showing [crown][cross][MB][&S]. My guess is that the "MB" is Mappin Brothers and the "&S" is Willian Sansom & Sons who partnered with them in 1846. I'm not really sure about the crown and cross. I can't find a similar hallmark to compare it to so this is all just a guess on my part. Pics below.




I see no signs of the platting wearing thin like I'm used to on electroplate, however it seems to be made of two pieces of silver "sandwiched" together which can be seen while looking at the edge of the tray hence my assumption of "Old Sheffield Plate" rather than solid silver.


Up close details. After searching for "Mappin Brothers silver" on a popular auction site I found a few pieces with very similar beaded edges.



Thanks for looking :) any information at all would be much appreciated!

[Shofner303]

If anyone can even help confirm if it would be considered Old Sheffield plated or if it is electro-plated it would be of some help. I really have no experience in silver plated items.