Thanks tessagin. The mat used to belong to my grandmother. When she went into a nursing home she decided she didn't want any of her sewing things anymore, so she gave me the lot! Sewing machines, embroidery machine, mats, rulers - the works. I'm thinking it would be about the same age as yours.
I don't use it often, as most of my cutting out is done by hand. I noticed the warp last night when I went to cut out some strips. I plan to make a bed runner for her to say thank you and that all the things she gave me are being put to good use!
I didn't want to risk the fabric cutting wonky, so I painstakingly drew up and cut by hand all the strips last night!!!