The easy answer is, first, poke a hole in it with a screwdriver. Then pry it out. . . . . . But to be more helpful, I'm thinking those sight glasses are pressed in there. I'm not sure it's wise to re-use them, either. I don't know this for sure, but I'd get ready to buy a new one. Then get a socket that is the right size and putting it over the sight glass from the outside, tap the socket with a hammer until the glass pushes out. To put the new one back in, just reverse the process. Okay, now I'm waiting to hear from someone else if that was a crap answer or not.
Just leave it in. Both Hiero and I left our sight glasses in and no ill effects to the rubber OR the glass itself. The powdercoater will reccomend they be taken out, but just tell them to leave them in. Before they powdercoat the cases they will mediablast both sides, so when you get them back make sure there isn't residual media on the inside of the cases. I just washed mine out with an old toothbrush in the sink before I stuck them back on.
Post up any more questions to this thread... Hiero and I bounced a lot of questions back and forth via PM which would probably be helpful if they were actually in a thread so other people could read them.
It's an easy mod man.
Sounds like we need a powdercoating FAQ!
I pulled the rearsets AND valvecovers/camshaft covers off and had them powdercoated as well...
what your powdercoater media blasts is going to be up to what he normally does, so ymmv on that, mine didn't blast the inside of the cases and I agree there's no need for that. I went ahead and washed the inside out a couple of times though just to get any residuals that may have worked their way back there...