Does anyone know what Post Office would have the postal mark: NNJ Metro P&DC 076?
What you have is a note telling you where is was processed, not where it came from. “P&DC” means Processing and Delivery Center, which handles mail for an entire portion of the state of New Jersey. “NNJ Metro” just means Northern New Jersey. That center handles mail from Newark on down to South Plainfield, and so many towns you wouldn’t even want a list. Plus the letter could have been dropped by somebody just hopping off a plane from Newark Liberty too. You need to look deeper, like for a meter/postage mark, but you would only see that if an electronic meter or internet postage had been used.