Visiting the Past

I Photoshoped this black and white picture of my Dad and me to give him when I went to see him today and he loved it. It’s funny to see Dad in a hat, but I remember men wearing them when I was a child.
Customs certainly do change, don’t they? Sometimes it’s hard to believe I was born before TV, cell phones and the Internet. No wonder my brain is fried at times. It’s all too much to take in.
I suggesting going to Swiss Chalet for dinner, which is where we went as a family on Sunday nights for a treat. While we were eating, I told my dad about the time I went there on a date. When the bowls of water with slices of lemon to clean your hands arrived, my date drank it instead. Dad thought this was hilarious, and when the bowls arrived at the end of our meal (some things don’t change), we both burst out laughing.
Dad was up until 2 a.m. last night trying to find the answer to a puzzle, so we worked on it together and still didn’t come up with an answer. The puzzle is: You have 12 identical looking coins, one of which is counterfeit. The counterfeit coin is either heavier or lighter than the rest. The only scale available is a simple balance. Using the scale only three times, find the counterfeit coin.
Dad says not to hesitate calling him at three in the morning if I manage to figure it out. Any ideas?