I have no recollection of them implementing stock bolt shortening as an armourer's instructions after a certain time, except with the indians. If it were implemented then Lithgowicon's after 1940 likely would not have come with the square or the plate, but they did. Also I don't know of any kind of varnishing done through FTR's, unless during the FTR they applied an extra coat of linseed which has stuck to the top and gone shiny (which is very very unlikely). Could be someone's target rifle where they refinished it and ground the bolt down. What about the bolt? How did it come out?