I collect headlamps. Carbide lamps of course but also early electric miner's safety-lamps, various hunters' lamps that were popular among cavers when my father was active in the sport (sixties-seventies), and some from back when I was younger and just getting into caving myself (nineties). I've got a shiny Thomas Edison Model P from the thirties (complete with one of the weird Nickle-Iron batteries that Edison was fond of), and various models by Koehler, Oldham, MSA (Mine Safety Appliances), etc.. I also have almost every version of the Petzl Duo (including the Petzl Explorer which is a Duo integrated into a helmet and paired up with their last carbide lamp), and at least one Petzl Zoom with each of the battery box configurations that they offered over the years (the old 1xMN1203 4.5v cell version, the 3xAA back-of-head, the belt-pack-or-back-of-head 3xC or 3xAA, the fabric belt-pack 4xC, the 4xAA that used the same battery box as the Duo, etc.).