I found this little square amongst a lot of engineering tools I bought recently. In 1880, J Grant has made a lovely job of making a small engineers square from an old saw plate. He has thoughtfully used the part of the plate that has a portion of the saw makers stamp on it, so at least I know it once was a saw. As the only 2 letters of the name visible are 'ON', I reckon I've got quite a job if I want to identify the saw maker.
Rob Very cool It will be esp. hard to figure out if it is "..... & son". There were a lot of those. enjoy Joe S.