Cactus / myriostigma

This is an Astrophytum myriostigma v nudum cv khoyo.
I bought seeds and sowed on 08/10/2003.
Young seedlings were grafted and derafted  after grow to flowering size.
Khoyo turns body color during juvenil but stops turning body color when the plant was a mature age.
This one is a mature age plant but it shows a hint of khoyo character.