Hi, the piston washer on that model B might be an original one. It looked intact & was supple so I didnt replace it & it seems to work pretty well. I tend to make them if I need them. It's a bit of fun if you have the time & the bought ones sometimes need conditioning & fitting so I end up fiddling with them anyway. Your woodwork looks to have cleaned up well. Some stocks have marks & large patches which are almost black in colour & are really deeply ingrained. They can be got out but it's often a long job to do so. Yours looks to be pretty good.