1776 1/2 Reale

Hello everyone. Well I've been lurking on here for a couple months now and finally got something today worth mentioning. I was coin shooting at one of my favorite parks this morning when I was approached by 3 dogs and their owner. She said hi to me and obviously knew what I was doing. As she passed me while walking her dogs, she said "you know they just tore down an old house a couple blocks away from here, I know the people who live next to the house that got torn down, just tell them I said it was okay for you to hunt there". I thanked her for the information and drove to the location where she told me to go. when I arrived, the remains of the house were completely removed and there was nothing but soil left. I spent about 40 minutes searching the 50' X 150' plot, locating nothing more than a couple of clad coins and some old metal building materials. I started on the last swath of ground before heading to the car. Towards the back of the property, I found an aluminum token that said "good for one cigar". It was pretty corroded due to the fact that the area I was hunting is only about 1/4 mile from the Gulf of Mexico. I dropped it in my pocket and continued working my way towards the car. Almost up against the sidewalk, my ace 250 gets a strong silver signal 2" deep. The ground was still very loose from the excavating that I dug down by hand and immediately saw a glint of silver in the soil. I picked it up and my first thought was I found a Canadian dime. After carefully removing some of the dirt from the coin, I confirmed it was indeed foreign but not Canadian. I flipped the coin over to look for the date and I almost passed out. I saw the 1776 and thought I was seeing things. Since I had no idea what I had found, I quickly finished detecting and drove home to gently rinse it off so I could identify it. It is a 1776 Spanish 1/2 reale. It was minted in mexico as indicated by the "O" over the "M" on the reverse. I took it to one of the local coin dealers, and he told me it was only worth about $5 since the obverse had some tarnishing on it. I'm not sure if he was trying to BS me or not, but I'll be getting a second opinion about that next week. I used a flashlight in the photos to help cut through the tarnish on the front, that's why the coin in the photo looks like it's copper. Can anyone give me an estimate of what something like this is really worth?

This is by far my best find to date. Happy hunting!

Joe