Thermoplast 2 prong keeper used with 14988 Vinyl Patio Sliding Door Handleset 

This Dual locking keeper / lock has a a sliding bar that travels up and down and latches onto the 2 prong strike
Then the white cover plate fits over the top of sliding lock bar to give a finished look

The old style is replaced with a current model 14361 and uses a different handle and keeper

Replacement Option 
14361 - Handle set, 6-9/16 screws, with keeper 
A- Measurement is 1-1/8" or 3/4"