No feet on your kettle? I would date it to a time period when cook stoves were being made, later half 1800s. Kettles and pots with legs were for hearth cooking, being earlier.
If the legs are broken off, it might because the early owner wanted to use it on his / her stove top. Also if it did have legs, it very much be earlier.
Dating is by the style and shape of both the legs and the handle ears.
I would date your lid in the same time period. Very hard to narrow it down, unless we all knew a little more.
Fancy handle. We need to remember that foreign pieces were imported into this country. I have never seen a fancy handle like yours on an american piece, but have seen your gate mark style on an american piece. But I have not seen it all
I am inclined to agree with you that the (not orange) lid is for two kettle sizes. Looking at the lip on the underside of the lid is quite wide. Thinking that the ring went on the outside for the #4 kettle and on the inside for the #5 kettle. Make any sense?
Just my thoughts.