Welcome to the forum!
Yes, Nick is right; you need to define what you mean by "disk"? The take down is not a disk or disc, and the unit disc in the RS would be unusual for a property marked rifle.
While a Danzig/17 could have a manufacturer original stock with grips, but no take down (have a unit disc instead), it depends on the rifles range. It would be unlikely for the rifle to have stayed in German service, obtain a property mark and not somewhere down the line get reworked and not get the take down added. The vast majority of rifles that stayed in German hands were reworked, some a number of times, usually if the rifle stock didn't already have a take down, the ordnance shops would have added one. It is possible of course, but unlikely.
It is also unlikely the stock would be the factory original one, you do come across them, but most were replaced, at least so far as the trends work suggests.
So, yes, if it is property marked it should typically have a take down, and typically, but not always the stocks are replacements, not "factory" original. Generally if the stock is period to the German service, it is considered matching though.
Hello
I've tried looking all over to answer this question for myself but I haven't been able to find anything. I've seen a few pics through google searching of some Gew 98's without the disk. Is it normal for a Gew 98 Danzig 1917 with the 1920 date stock to NOT have the disk in the stock? Does that mean it's a replacement stock?
Thanks.