Information For An Obsolete Flow Meter

I have a flow meter made by Osmonics Phoenix Operations.

Model 491

Serial # 3A774603

i don't have a manual for it

the company does't exist anymore.

Its currently programed to read a 3/4" propeller water meter.

i need to reprogram it for a 2" water line.

i would appreciate help from anybody who knows anything regarding this device.

i really would like to get my hands on a manual for it.