Hi Grumpy, no,I have never seen that belt set up before , then again, I have never clamped my eyes on a Model 590 before...the pic you posted may be a Model 430 Diplomat, which, one would presume be the same as a 590....but, there may be differences between the two....
I cannot see the holes drilled for the handle...I think this may be a different set-up entirely....
I will make some inquiries early tomorrow as it is a bit late now.... wink
cheers2

Please do not PM me asking for support. Please post your questions in the appropriate forums, as the replies it may receive may help all members, not just the individual member.
Kindest Regards, Darryl grin