Oh, I like it. I don't know if it's balanced, but it has to be somewhat reasonable. Lets you hit any one drop, at the expense of not helping at all with 2+ cost spells.

Vintage will love you for this. But, yeah, seems reasonable to me.

Yeah, I was thinking that any any-colour-on-turn-one land would be very very welcome. But it's probably comparable to Gemstone Mine, so probably ok for eternal formats.

Heh. I thought of Three Card Blind :)

Heh, yes absolutely ideal in any format where you only want one land. But for normal magic, it's pretty underwhelming.

Come to think of it, it fills a similar niche to the Copperline Gorge cycle, in letting you splash 1-drops. But those let you splash 2-drops and 3-drops as well, and still act as mana fixing at higher costs. Whereas this only helps on turn 1, but doesn't slow you down.

So I guess you most want to play it if you had an almost mono colour deck that wanted to splash a one-drop which was really, really useless on turn 2? But I don't know how much that happens.

This also color-fixes on turn 2: tap it for mana and float it as you play a second land.

True, and after the first two turns it's still providing colourless; where the gemstones and Pentad Prisms run out completely. Probably a fair card with some good uses. I don't think I'd run it in any old deck; but it does help make multicolour decks a little bit more reliable.

Now you mention it, the more apt comparison probably isn't Gemstone Mine but Tendo Ice Bridge. This is slightly worse in normal games because you effectively only get to remove the counter on turn 1, but it's better in unusual circumstances (like 3CB) where you have just one land for several turns.