that serial number belongs to the lot that was 127 made in 1925. So I'd say it's likely a sphinx decal, which is about the most common one you can find. So unless it's in wonderful condition (and NOT for it's age, it needs to look almost new) it's not collectable, just a neat old machine to have and use. It is very usable, and parts are easy to get.
And since you say "old rusty" then if you can get over $10 for it, you are doing well. Now if the table is really nice, you might get $50 if someone wants to put a different machine in it, but only if it's one of the more sought after tables in very nice condition. And another note - if she's got the bench, it's probably worth more than the machine and table. Benches are much harder to find.