R12 Oil charge

[bdgr]

Going to have a friend of mine charge my AC system this weekend, I managed to aquire a few old cans of R12...and one can of oil charge.

Now, back before we found out it was evil to service your own AC, I re8member oil charges being little cans, labled with the amount of oil and the amount of freon in the can. This can is a 14 oz can, the same size as a regular freon can and it says nothing about how much oil is in the can.
this is that is on the can as far as details:

Replace a small amount of oil in a GM system convieniently

Directions
Oil charage is dispensed into system as regular R12. Simply insert container with approved dispensing valves, using proper gauges and charge directly into system.

Use in inverted position only

Then a warning about not connecting to the high side or setting on fire and stuff.

it's napa brand, and napa part number is 20 9507.

Anyone remeber cans like this? Any guesses as to how much oil is in this critter?