i'm using bitcoin core. my backup is several years old. when i dump the wallet in the folder there are no addresses in the client. but i am still receiving BTC from my OG address that is no longer displayed in the client. but again, i backed up the wallet AFTER those old addresses were generated. this new address was created and the hard drive was formatted without creating another backup after that new address was created. that address is out there in the BTC world but since i did not backup the wallet after i created that new address i'm wondering if the client knows it should direct those coins to my wallet.
For test whether address is yours or not, when Bitcoin Core using your backup wallet, open the console and type validateaddress "bitcoinaddress"
One of the result is "ismine" : true|false, (boolean) If the address is yours or not.
Without running this command (or sending some coins to the address) it is hard to give you definitive answer whether your old backup contains private key for the new address you created later. The reason is your old backup contains also next 100 private keys that going to be needed later, this mean for new change address when you sending transaction or when you add new address to receive Bitcoins to. So you have to ask yourselves how many such operations requiring new address you made since you make your old backup. If its under 100, you should have the private key in your backup.
