That hub appears to be a Shimano 600 6208 Uniglide variant (or an Ultegra 6400 “tri-color” I can’t tell for sure from the photo). It could be a 6/7 or it could be a longer 8-speed Uniglide one. The outer 2 cogs don’t thread into each other as you suggest, just the outer cog threads onto the UG freehub body to act as a lockring cog. That 2nd position cog should just slide side to side on the splines. Correct me if I’m wrong here.

PS: Doug, - thank you for putting proper down tube braze-on bosses and top tube guides on my Puch Marco Polo then repainting my frame a beautiful Indian Red metallic Imron paint color some 36 years ago. It was sent to you from International Pro Bike shop in Bellbrook Ohio who I believe contracted out frame repainting and repair jobs to you at that time. That was the loveliest, most durable paint job ever and I took really good care of that bike which I still have but have not ridden in a few years.

Do do you still accept frames for repaints? Just checking. Also, is Imron even used any more? (Sorry about going off topic).