I don't think it's a tomato. It looks like celery to me.

Sorry about the picture quality but here it is as of this morning... making another shoot, I meant to say earlier. It just doesn't seem to be making any "normal" seed leaves. And celery is one of the few things I think it can't be, I don't have any seeds and don't think I've composed any in a long time if at all. Looks almost carrot-like now but I didn't have the carrot seeds out either...

As you say it doesn't look like a seedling at all. I'm guessing that there were carrot tops in the worm bin or outdoor compost and that's what's growing here. The compost looks a bit wet btw.

its not a tomato ...

but just give those old seeds some time ... dont give up ..

as to this seedling.. let it get a few more leaves.. and then crush one.. it will either smell like a tomato or not... or celery.. which was my guess also ...

i gave up on wooden name tags.. as they tended to rot.. and added the potential for attracting molds, mildews and fungus to my seedlings .. as they rotted ...

plastic knives ,.. lightly sanded.. and carbon pencil... are forever ... as one solution ...

ken

Actually, update, just checked when I got home and normal-looking seedlings are coming up. So the old seeds are still good (I'm a little surprised) and also the mystery thing is still growing. Still accepting bets about what it is, I'll keep it going and see.

The marker was just a scrap thing in a hurry...

Another possibility is fennel. Did you throw some trimmings on the compost heap last year? Your nose should tell you if it is carrot, celery or fennel. All have distinctive smells. I don't think it's celery - the leaves seem too finely cut to me
Personally I'd get it out of there because its roots will compete for space with your tomato seedlings and it is unlikely to make a usable vegetable.

Oh, fennel is an interesting guess, that could be possible although I don't remember having any around recently. It doesn't smell yet, whatever it is. If you think it will fight with the tomatoes I'll pull it up; they're looking pretty happy now.

Thanks for all the help, everyone.