To replace, or not to replace

I am constructing a greenhouse in a previously unused space. The windows on it are quite old and I am trying to decide between replacing them or not. I have a picture of an unrelated broken pane from the window.

My specfications are maximum light transmission and the covering to not be clear for privacy. It also must be rigid (ie. no plastic sheeting). The currently existing glass seems to have tiny ridges in it, and is fairly thick. It permits light through, though it is discoloured and resists cleaning; i wonder if I could do better. Also, what is this glass?

Its not a large area that needs to be covered, so expensive items can be on the table.

Any advice would be greatly appreciated.

Gosh, that glass looks awfully nice. I'd think power-washing them would go a long way. Also, maybe try using TSP or some environmentally appropriate alternative. Vinegar and baking soda?