I just got one of these, it arrived today! Mine has the standard 1/4 inch dia shaft and not the "knurled" one
as showin in the photo (of a different 250K unit).
http://cgi.ebay.com/Attenuator-24-Step- ... dZViewItem
I doubt that I could have built one myself for the total cost (39.95 including the shipping).
He has these in 250K and other values as well.
/ed B in NH