Good to know Trevor. Thanks for that infoI belive that from the introduction of the Slimline frame in 1960 to 1962 (?) there was a Dominator Deluxe model that included side panels and an enclosed chain guard. I have a 66 Atlas frame/swingarm that has the same bosses you describe. According to what I've read from the NOC (UK) they just continued putting the bosses on after discontinuing the Deluxe. (Photos courtesy of the internet, not mine)
Also that’s some interesting looking Atlas!Good to know Trevor. Thanks for that info