I see someone on eBay UK regularly sells the brochure with sectional diagram, parts list and maintenance instructions which originally accompanied the MkII. I got one for £0.99, though they may go higher sometimes. Unfortunately my sole infraction on this board was for showing people an eBay auction - all very courteous, with an explanation that they knew I meant no harm (or, I suppose, profit). But it is easily findable.
I don't doubt there have been developments in target rimfires in the last fifty years which bring a very slight edge to a tiny minority of top-class target shots. The 12/15 and earlier, perhaps not, but they easily equal 99 of the rimfires sold new. I think I know one current .22 which is a classic case of advertising revenue bringing editorial mentions, editorial mentions bringing popularity, popularity bringing after-market mods and accessories, and mods and accessories bringing... pretty much what lucky amulets used to.