old Russwin lever door lock

[Peter Martin]

I found an old Russwin door lock. Single lever. The inside cover and body both have the number "351" stamped inside.
The lever springs are still strong. I may be able to make a key for this. I presume I need the barrel/shank diameter and the bit length to begin with.
I can measure the height of the lever cut for the center key cut, and impression any wards.Pete
Pete
Sioux Falls