I paint a lot of older implements and have learned a trick just in case a decal still exists. Rather than trying to remove or replace, I just get some of that blue painter's tape and cover the area over the decal. Then I take my fingernail and rub the tape until I can get the edges of the decal to feel through the tape. Then I perfectly cut around the edges of the tape with a sharp knife, leaving the decal covered. Then I paint and when done just peel off the now painted tape to reveal a perfect decal underneath with perfectly sharp edges. Even if the decal is a little old and ratty, it still looks pretty good.