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Could you provide a picture of the Radio and a picture of the manufacturer label?
For this particular type of paintings, it's not always needed to have Certificate of Authenticity. Basically, nobody is going to replicate a 200$ paintings, it will be better to replicate a more expensive painting.
In any case, if you want to get the COA, I can provide a list of appraisers that can authenticate your painting. However, be sure that the authentication fee will be in the range of the paintings value, so most likely that a COA won't be worth for your paintings.