To return to the O.P., I would immediately offer the Serial # to a potential buyer. No problem at all. Since I know I’m not selling stolen goods.
I don’t buy new cell phones. I’m weird that way. I buy used, and ONLY on Craigslist. I’m in NYC. I have my pick and choose of almost all models of used devices.
I send an email and ask for the IMEI #.
And a photo of the sticker.
They agree, I call Verizon or do it online, check for theft, go buy the phone. I always take a jeweler’s loupe with me. So I can check the IMEI # inside of the phone. They don’t want me to check it, I stroll back to the subway.
I’m leery (my first instinct was to spell it “leary,” but Google tells me that spelling hasn’t been widely used in 100 years. Huh.) of giving out a serial number, and Ebay is different from Craigslist in a lot of ways, but also - you ask questions before you agree to purchase the phone, which would be absolutely fine with me. My only issue was that we had gone through a week-long auction during which the buyer asked no questions at all, and minutes after he won, he started asking for additional information.