Congratulations Klinga! Nice find.My earliest coin was a 1945 penny.I've used vinegar with some success,haven't tried cloudy ammonia but will give it a go.It's great finding spendable coins-you can use them to recoup the cost of/upgrade your detector or buy other detecting accessories, but it really becomes interesting when you start pulling up other stuff(pre-decimals,jewellery,relics) and then researching them.The research and history of these items becomes another enjoyable aspect of this amazing hobby.The priceless part is the time you'll spend with your 7yo.Take him/her with you whenever he/she is keen - out in the fresh air,exercise and more importantly you'll have a whole new world of experinces,stories and memories to share.They grow up fast and may not want to continue when they're older, but you''ll both always have those memories/stories.Have fun with this awesome hobby.