Thanks to David Spragg for the following link which identifies that (on page 17) the Harlequin Club and Casino is listed as part of Cambridge's 1960's local venues. This would suggest (to me anyway!) that this was a casino operation rather than a university fraternal club as currently listed in the chipguide.

http://www.i-spysydincambridge.com/assets/pdf/booklet-march2011.pdf