This is a box of vintage Brico piston rings. Brico traded under various names it seems or had various names from Brico to Bricovomo to Covomo and were an British piston and ring maker back in the day. These are marked as R.837 and on the outside it gives the sizes as follows:
Diameter is 3 and 5/16 inch which is 84.14 mm in metric.
Ring thickness is 5/32 inch which is just under 4 mm in metric.
from an old Covmo book it lists the cars these rings were originally intended for which include Buick, Chevrolet, Vauxhall, Bedford and International. There are various models listed between 1929 and 1939.
In the box are nine new rings. Presumably a set or part set depending on what vehicle is involved. Obviously if you have or own or are restoring one of these antique cars or trucks, this box of new rings is worth having.
Postage in the UK is £ 4.00