Admiral PR280R transistor radio with handlebar mount

I found this radio in my Mom's closet when we were cleaning out her house. I can't find any information on it, but it works well and doesn't look like it was ever mounted on a bike. It has a special key that can be used to remove the radio from the handlebar mount when you are not riding and an 1/8" headphone jack in the side. The model number came from a paper slip the inside of the battery compartment, but has no date of manufacture. It looks mid-60's, but not being a collector I don't really know. Any more information someone might have would be appreciated.