From an email to Repeater-Builder.....

From: (Deleted to protect the source)
Subject: Info on the SR251 key

Hi there. I work in a hospital lock shop. Last week I was given a lock from an old electric panel and asked if I could make a key for it. It had a code SR251 so I looked it up in our key code program but there was nothing listed...

So I tried to make a key using the locksmith method of impressioning. The lock had been filled with paint many years ago and after many applications of "Goof off" and some high pressure air the lock was still not cooperating.

I went to Google and after several attempts came to your page and found the picture of the key. It was very easy to read the cuts from the picture and the key worked the first time, thank you very much. Here is the Locksmith information that goes with the key, feel free to include in in your posting.
Key: SR251
Cuts are from bow to tip:   12342
Blank is an Ilco Y13, 01122R
HPC card is #55

Thanks again, keep up the good work.

(Name and callsign deleted, at his request, to protect the source)

THANKS to (name deleted) for the above info, and thanks for taking the time to write.

From another email:

Subject: NSR251 key
From: (deleted)

On the "keys page" you ask about the NSR251 key and its relation to the SR251 key. They do appear to be the same. I don't know what the "N" is for, but my own weak guess is "National" since they have the shape of National keys.
Attached are two photos. The first is from the Square D catalog.
The second is pictures of an actual NSR251 key, front and back. This one is stamped from sheet steel (it's magnetic) rather than being cut on a brass blank. This suggests they make a lot of these, for the cost saving to overtake the cost of making a die.

Thanks to JRK for the email and the photos.