Oooh, very interesting. I've always really liked little ProAcs (I've owned Tablette 50 Sigs and Ref 8 Sigs). Without the port they could be something very special indeed. I know Stewart Tyler was playing around with a modern LS3/5A variant on eBay under the Celef brand a few months ago (I think it was basically ProAc drivers in a proper LS3/5A cab, e.g. with grilles etc). I guess this is the proper commercial version. I'd like to hear a pair sometime.
PS Great to see some choice in infinite baffle mini-monitors, from memory we now have the Falcon LS3/5A, the Stirling and Graham variants, the Harbeth P3ESR, Spendor S3/5R. Now imagine how cool it would be to stick something like this in a nice low-mass non-resonant cylindrical metal cabinet...