HA is Atkin Brothers and the hallmark is Sheffield, 1910. HA stands for Harry Atkin. This piece is actually a hot water jug rather than a tea pot and would have been the fourth piece in a 4-piece tea service (teapot, creamer, sucrier and hot water jug - for topping up the pot).
The other mark is GN over RH for Nathan & Hayes (George Nathan & Ridley Hayes) and the hallmark is Birmingham, 1894.
For values I suggest you check out the completed auctions pages on eBay. For a lowest possible value you can use the scrap value (Google “scrap silver calculator” and remember that sterling is .925 pure).
If you do decide to sell make sure to polish them so that they look their best.