70 Cuda Front bucket seats seatbelt with lap and shoulder buckles

[HemiRod]

My 70 Cuda has date code 1969-3 on the original belts in car.  Missing the 2 lap and shoulder buckles. I have seen a couple and their labels say Chrysler Corp 2999585 and code F 3569.  I checked in 70-71 Chrysler parts catalogue and this label number is not there.  The 4752 is the part number. what does F 3569 mean.  I thought it may be 356 day of 69.  However, I saw another with F 5069...only 365 days in a year, so I must be wrong.

Please help if you can.