Your "Great Seal" button has a raised rim/border, so it is post-1910, but it also lacks the "black finish" used in the World War One era and a bit after. So, it dates from approximately the 1930s to much later.
If you could clean the back to see if it has a backmark (maker's-mark or supplier's-mark) and if so, tell us what it says, we might be able to narrow down the date-range.
Just a word of caution....in the future please for your sake,before you electrolisis anything,especially a button,find out what it is,and what the value may be is FIRST!!!!
Kuger gave you a wise caution-note. Electrolysis, and Zinc-&-Lye Bath, are wonderful for removing the rust-crust from iron, but will remove gold-plating and silver-plating from buttons.