When you are looking at Bourns Gas Discharge tubes from the 2003 Series the part numbers will break down into 5 sections. Here is a breakdown from the data sheet.
Using this guide we can take part number 2003-07-SM-RPLF and we can break it down as follows.
2003 - Series
07 - 75Volts
SM - Surface Mount
RP - Part comes on a reel.
LF - RoHS compliant part.
Applicable Part Numbers
2003-07-SM-RPLFTR-ND 2003-07-SM-RPLFCT-ND 2003-07-SM-RPLFDKR-ND 2003-09-SM-RPLFTR-ND 2003-09-SM-RPLFCT-ND 2003-09-SM-RPLFDKR-ND 2003-23-SM-RPLFTR-ND 2003-23-SM-RPLFCT-ND 2003-23-SM-RPLFDKR-ND 2003-35-SM-RPLFTR-ND 2003-35-SM-RPLFCT-ND 2003-35-SM-RPLFDKR-ND
2003-07-SM-RPLF 2003-09-SM-RPLF 2003-23-SM-RPLF 2003-35-SM-RPLF