Silverplate Tea Set

[YorkiePud]

I have just recently aquired a tea set from my Grandmother. on the base it's markings are :
Stamped J B & Co Ltd
Sheffield
Silverplate
M642
Aswell as this on all three pieces 11/17 is scratched onto it.
I have tried to find out who J B & Co is but can't find anything. Does any one know who J B & Co might be, what the numbers M642 means and any websites where I could possible date these.

[2209patrick]

Not sure this is the same company, but John Brown & Company, Sheffield, England (1897-1932) used a JB&Co mark on their silverplate.

Regards,
Pat.