I don't think a pricecheck for a collector's item can be done, you should just ask for keys metal and offers and see how far it goes, but with collector's stuff random is random, if it was a glitched item you could score high, but with levels you might get a plus, but not sure how much more

Thanks, because i realised I also have another lvl 1. Ill keep that in mind.

As a general rule, and not trying to be rude here, unique odd levelled items are not really collectors items.
There is an endless stream of them flowing into the game, from crafts and drops, so they don't receive the same colossal increase in value that say, level 0 vintage hats do. Vintage items are much more collectible, because there is a limited supply.
From a quick look around outpost, the general consensus seems to be 6-7 keys for a LV 1, which is what sellers are asking for. Lv 1, 42, 69 and 100 generally only add 1-2 keys on unique miscs, and 1-2 ref on unique hats. Obviously there are exceptions (TC) but that is the general system, at least from my viewpoint.

Ok, thanks.