Both of those part numbers are Bosch. Just one is the "short" number,
one the "long" number. You will notice that 13953 is a derivative of the
long number. They used the last four digits and placed a "1" in front to
make the short number.
Regards,
Hal Rogers
H.D. Rogers & Sons
Import Auto Specialists
3418 Barksdale Blvd.
Bossier City LA 71112 USA
(318) 742-3651 phone (318) 742-5044 fax
http://www.hdrogers.com