Panch So Panch(505) & Panch so Saat(507) are common term used by A/C Walas because they are coming since Long.
even i have installed in various cars, the compatible model by Lianden 505 but still a/c wala used to call it Sanden 505 or 507
Yes, 505 & 507 specific are piston based and built for R-12, their same series models for R-134 have model numbers as SD5H09 & SD5H11 respectively
If it is written simple SD-505(It automatically means R-12 series), Series like SD5H09 represents R-134 where "H" stands for Port Location "Head"
If it is written SD5B09 it means Port Location "Body"
Correct amount of gas & related calculation r present with Technical sheet comes with compressor packing.
If you are in Karachi, i can refer you Technical guy who is importing Sanden & Lainden compressors,you can buy only compressor from him too and do rest of work by your trusted A/C Wala or you can do all work work by him