That model has been obsolete since 1982. You might find a scanned copy available on one of the gun auction sites or eBay.
Try eBay
You can find an owners manual for a Savage Arms Foremost model 6670H, 12 gauge shotgun by contacting the company. The phone number to call for the manual is 413 642-4261.
Glenfield,which was made by Marlin Firearms Company made a bolt action .410ga shotgun from 1956-1965.This was the marlin model 59 which is the same shotgun as your Glenfield model 60.
Go to http://www.marlinfirearms.com/ and request an owners manual for the marlin glenfield model 60. They have changed little since 1980.
Your shotgun is a Mossbeg 500. made by them for Sears. Go to the Mossberg website, customer serivce, owners manual, and download the manual for your shotgun.
Try gun shows.
Yes, there is an owners manual available for a Charles Daly Model 500 double barrel shotgun. Various sources can be found online.
This model Cross refernces out to a Remington Sportsman 58, introduced in 1956, the Sportsman-58 was Remington's first gas-operated shotgun. You can request an owners manual for obsolete firearms at www.remington.com click on sportsmans library, then downloads, then owners manuals, then click obsolete owners manuals, you will have to register but it is worth it to get the free manual.
Try want ads and on line auctions.
A guy on eBay has a store called Rediscovered Shooting Treasures (RST). He sells reproductions of the Marlin Model 120 manual.
Do you have the pump shotgun or the lever-action rifle?
Look up the Marlin shotgun with the same model number.