How can I tell if a back glass already has triple thick?

[DRANO]

Hey guys,
I'm a bit new to EMs. I just bought my 2nd wedgehead in 3 weeks (Gottlieb Spin Out).
The seller told me that he thinks the back glass has already been treated with triple thick. I plan to do some touch up work and wondered if there is any way to verify this? And, if I'm not sure, would it be okay to apply a coat anyway? I'm assuming the answer is yes, but better safe than sorry.

Thanks in advance!
Adriano

 

[Menace]

Usually you can tell if a glass has been sprayed by looking at the score windows for overspray or any ridges where they masked them off. As for the other part of your Q, hopefully someone with more experience will chime in.

D

 

[novaguy]

Another way is to look at the back side of the glass under some light and look for dry areas that might have occured during the application of the TT.