Some of the print heads are from functional printers, some are from defunct printers kept for spares, some are from printers under repair. I collect good old Canon printer models. I have found several printers in electronic waste containers, at flee markets and thrift stores. I have also bought some defunct printers cheaply from colleagues and got some for free from family and friends. I have been able to repair several printers others had given up on. The only Canon printer I bought at a store at regular price is the iP4200, when it was introduced.
Here is a list of my Canon printers.
Fully functional iP's 2700, 3600, 4000 x2, 4200, 5200, 6600D. Under repair iP 4300. Defunct, kept for spares iP 3000, 4000 x3, 4200, 5000, 5200R
Fully functional MP's 280, 540 x2, 970. Under repair MP110. Defunct, kept for spares MP610.
Fully functional i965, defunct i560 and i990.
Fully functional MPC 190.
I also have a handful of HP's.