I can't think of this phrase..?

Question

It's three letters then two numbers, like an exclamation. "___ ##!"

It has to do with fleeing from the police or police in general, and it originated in the 1920s I think. This has been bothering me for awhile. If you can figure out what it is, thank you! :]

Answer 1

This isn't what you described, but is it 10-4? :)

Answer 2

23 skiddoo. Also not what you described.

Edit: glad to be of service. Four hours after the time you posted the question you'll have buttons to choose the best answer.