This is a tea set made by William Shirtcliffe and Son Ltd of Birmingham, England 1921 when the company became Ltd. and used the SL in a shield mark. The signpost mark was used by this company as well as William Suckling and Co of Birmingham.
The EPC indicates that this is not sterling silver but Silver over Copper.
The other numbers are pattern and shape numbers for the set.
This set would have a value of $175 to $225.00 USD retail.
It is important for you to click the stars after you have read this answer.