I've got a really nice, for used, plastic reservoir that has the date code still intact. I've never seen a date coded reservoir before but its a little bit dirty and slightly yellowed but really not much. Whats a good way to clean this WITHOUT removing the ink stamp? I did a search I didn't find much other then some differing opinions on bleach, peroxide, ect. Thanks for any and all help? P.S. I'm wondering if the solution that people use to restore build sheets would work and if so, what is that solution?