Hello,My name is ***** ***** I would love to help. It would be irresponsible to answer without seeing the chalices and their marks to assess correctly.Please use the Add Files feature on your screen to add pictures of the item and any marks, labels or writing (does not cost anything extra).
This is a set of London England sterling silver and stag horn campaign beakers with monogram shield.
These were popular items in the mid to late 1800's.
The shape around the letter O that you described (and I am unable to see)
and the type style of that O will be the date code. I am adding three images of the possible date years and you can determine
the exact year of your set by comparing the images and outer shapes for the letter O.
The maker's mark seems to be too worn to determine in this case.
The value of these will be the same in any date from the 1800's.
Each cup has a current value of $700 to 900USD or 480 to 620GBP.
Here are some examples of similar for you to view by clicking here.
It is important for you to click the stars after you have read this answer.
Here are the date codes.
Date code 2
Date code 3