If you hold a regular bill in your hand and look at the picture you can tell the serial number is lower and the seal below it is lower and to the left. Normally it's bottom is lined up with the bottom of the word 'one' and the right lines up with the 'E' in 'one'
Another cool radar in the register today. 36666663... Rougher shape though. Also last week I managed to get a real nice crisp new radar fresh from the ATM in my store. I had been seeing all the fresh bills for weeks leading up slowly to the one I wanted and made sure to grab it when it got close enough.