Miller Keyless Lock - Identification/Age Question

[churchkey]

Hello All,
I received and old schwinn bike from my grandfather and locked onto it is a Miller Keyless Lock. I would like to know the age of it if possible. I believe this to be a later example based on the fact that the shank has the word "Hardened" on the front. On the back it says:

Miller Keyless Locks
Columbus, Ohio
Patents
1,825,467 1,929,598

On the Top of the case it has:
either 3, 8 or B and 2640

Can anyone help me out with a possible age and if possible any tips on getting it opened. I was told the combo is 4123, but despite trying that may different times, right zero, zeft zero etc... its a no go.

I would love to get this opened.

Thanks

churchkey