It’s a maker’s mark of sorts. The international Silver Company was formed in 1898 as a co-operative of more than a dozen New England makers who had previously been independent. Later they expanded to include a total of several dozen manufacturers. The company was centred in Meriden, Connecticut.
The intention was to increase their ‘muscle’ in the market place to the benefit of their constituent members. Many existing designs from the previously independent makers then carried the International Silver Company branding in addition to the maker’s own mark. Some of the pieces carry ISC’s name only.
The numerical codes on these pieces are difficult to attribute since they usually relate to codings that were internal to the company and for which the records aren’t good… dates, styles, ranges, makers etc. I’ve seen the 05038 mark on multiple pieces and I know that at least one of them was made by Rogers, but I don’t know if the code exclusively relates to them.
If you can confirm that there are no other marks on the piece apart from the ones you have shown, then seeing the actual piece might enable it to be tracked down from its style.
‘Silver Soldered’ is another way of saying silver plate, although distinct from ‘electro-plate’.
It weighs over 2 lbs so I wonder if it has any value. Thx! 
