Vintage Unbranded Barrel Key
Skate
Clock
Typewriter
For Square Stock
Used a digital calipers to measure inside dimension at:
3.81-3.82 mm
0.153-0.155 inches
I had previously and erroneously sold this as a key for an antique Hammond typewriter but it did not fit so I refunded the purchaser. So, please make sure you measure for your application.
Thanks for looking!