The old straight driver slot cutter design heads for older Philips Norelco shavers seem to not even be made by the Chinese clone heads makers any more. All the listings I could Google for HP 1912/2 and HP 1912/3 head sets were NOS items offered on Ebay at prices that seemed high to me. My oldest fully functional Philips Norelco is a corded HP1601 Rotatract that originally took HQ3 blades per Norelco tech support but current modern Philips Norelco HQ56 blades fit it and work. I believe that it is one of the earliest Norelco razors that used the triple point tipped spindles to drive the cutter heads. I also have a HP1318 Rotatract corded/cordless that has an identical head and overall appearance to the HP1601. It still takes some charge.