VMC300 Toolholder question

[Proteus]

Ok, I`m stuck here.
Looking at my toolholders for my VMC300, there`s a difference between them, and the toolholders at Coventry Toolholders.
(http://www.coveng.co.uk/group/covent...sy-change.html)
Mine has a machined groove in the top flange, and i do believe for my ATC holder(spring loaded fork). Se Attached Picture.
However the toolholders at Coventry has not :-\
Looking at the video on youtube, it seems they have 2 types. One With just the 2 notches on each side, and one With additional groove for a ATC Version With spring loaded fork.

Am i completely off track here, or is my assumption correct ?
Are there any drawings in some far away corner of the internet on these toolholders if i would make them myself ?
I could of course make my own drawing and plot it in.
They are a bit expencive if you need say more than 5-10pcs ER32 Easy Change Collet Chucks..

Any advice gents ?