@Gonnagetgoingreturnsagain Like you, when I resale handbags, I like to include certificate of authenticity, serial number, dust bags and receipts if I have them too. However, I have several of my mother's Chanel bags from the 80s and 90s, and most of them, I don't have any of the above. (The dust bags I do have have more or less disintegrated with age). That said, due to sentimental value, I wouldn't sell them anyway. Also, it's worth bearing in mind that some of the super fakes come with authenticity card, serial number, dust bag and even a store receipt, so they can be meaningless.
It's also worth noting that a lot of the Chanel bags of this vintage don't have serial numbers inside them. Indeed, have just been to check two of mine and neither have them, although one does have an authenticity card. I was with my mother both times these bags were bought - one from Old Bond Street, the other on Sloane Street, so know for a fact they are real!