Need Help Recovering BTC Mined Back in 2009

Hey folks. A client of mine has an intriguing situation. He says he mined some bitcoins way back in 2009. He showed me a backup of files dated to 2009, which got me digging deeper into this case, because it could actually be legit. My bad, I posted a wrong image earlier, but I fixed it now! https://prnt.sc/2690dbk I set up an old version of Bitcoin Core that he has, and when I opened it, I found a huge amount of BTC with details showing he mined those blocks. But as I was syncing with the network, the wallet balance suddenly dropped to zero, which made me think of a few possibilities about why those BTC disappeared. One thought is that he might have mined for real, but when the consensus was applied, another block got forged with a lower nonce, making him lose the right to the reward. As the app syncs over the years, the BTC that should've been in his wallet might be claimed by actual miners who validated their ownership, and as the blocks spread out, the rewards ended up in the wallets of the rightful owners. When I finished the sync and checked the wallet addresses in the app along with the transactions, I found 4 addresses but only one had any activity, and it was for a tiny amount, leaving the wallet with 0.00 BTC. Still, I thought I'd post here to see if any of you can help me figure out what's really going on and if he might actually be the rightful owner of that balance.

The image you posted shows that 5 blocks were mined on September 5, 2020 only in 44 minutes and 50 BTC were generated at each of them. The image is fake, because the information displayed can't be true. 1. Given difficultly of the network, it's impossible that someone can mine 5 bitcoin blocks in such a short time. 2. In September 2020, the block reward was 6.25 BTC, not 50 BTC.

Yes, this is fake and maybe it is a modified bitcoin core anyone can make a coin because Bitcoin is open source. Another thing it might be a self-hosted node install on localhost where you can mine 50 rewards for every block you mine or maybe the image above is edited. Why not ask the client and post the BTC address here and let us check if it's true or not. If it's true then we can provide a few suggestions to recover those BTC.

Sorry, I had posted a wrong image, updated now! https://prnt.sc/2690dbk

Just check all those addies with any btc explorer to see whether they hold any funds. https://www.blockchain.com/explorer https://blockstream.info/ https://btc.com/en

The image is still fake he only mined 3 blocks with a 50BTC reward each but the total amount balance is 312550? If you can share your client's BTC address here we can analyze or check the address if it has a balance or do what the above suggestion you can check it by yourself. Another thing that I notice is the color of the Bitcoin core wallet. It seems the wallet from the screenshot is edited or a modified version of Bitcoin core.

It's still fake. The image says that in 13/04/2009, there had been 3 blocks mined and sent to the specific wallet. However if you search this date, you'll notice there were no blocks mined in the 29th minute with sequence of another in the 43rd and 59th of that hour. Go backwards from block 10837 or to avoid this waste of time just search those addresses' balance.