Found one of them, sold it some years back.
I bought it in a rather tatty condition and refurbished her. She had the bolt safety slot mod, (two tabs welded onto the tube, above and below the the bolt handle slot, top tab also has a clearance slot cut through the spine, so the bolt could be physically held away from the breech face via a thin piece of sprung steel fed through them). I have seen a couple of others modified in this way over the years.
I don't know who modified them this way, I guess some foreign operator for safe vehicle transport, seems the most logical reason to me.