The balancer I have is stamped 17 B with B.S.I. initials. The balancer measures very similar to your S385-18 but does NOT have the wings
Paul from SWISCO responded:
February 22, 2017
If your attachments don't have wings, then you don't have the S385-18. See our S390-18 instead. This may be it. I would also recommend the 1720 option.