I had no problem finding datasheets for the SMBJ170A.
The first two datasheets I looked at (from different Manufacturers) both indicated that the "PR" marking indicates that the component is an SMBJ170A
Diodes Inc SMBJ Series datasheet
Littlefuse SMBJ Series datasheet
"PR" is also used by Bourns - the manufacturer you specified.
Bourns SMBJ series datasheet
Maybe some other manufacturer uses a different marking scheme.