I received a new WLAN grid antenna from a fellow Ham - thanks for this!
It is an HG2424G from HyperLink Technolgies Inc. The antenna grid is made of aluminium cast. The mounting screws are made out of V2A, the fastener for the mast seems to be made out of galvanized steel.
The antenna has a pretty good match at 2.4GHz - SWR 1.04:1 or a return loss of 33dB.