If indeed it is SN 77 the below prices are LOW. SN 77 was indeed made in 1929 and in mint condition would probably bring 5 figures at auction.
I've never seen anything like it. My Dad often dealt in high-end firearms. He always said rare firearms are a marketing problem. How do you find the one buyer in 10,000 willing to part with the cash? In those days, Dad relied on the ol' boy network - get the word out and eventually the buyer would come to you.
Dad never had the internet gun auction/sale sites. Nowadays a buyer can be located anywhere in the world. I can't imagine what that 1911 would bring.
If I were going to sell the pistol I'd talk to Randy Bessler -
Collector Firearms.
He once had a serial number '1' .38 Super priced at around $30,000.
coltautos.com If you would prefer to contact him by phone, his number is 703-281-6628