On the right side in front of the trigger
The Blue Streak has been in production from 1995 to present. If you want more Information I suggest you contact Crosman who owns both Benjamin and Sheridan. See the link below.
I've looked at every reference book I have and can not find a model Sheridan 63-90 Blue Streak. The Blue Streak, As far as I know, is CB9 not 63-90. On the CB9 the serial number is usually on the left side of the barrel just forward of the loading chamber. You may have to move the black rubber piece of plastic clip that covers the barrel.
In order to give an estimate of value I need to know the current condition of the rifle.Excellent to poor ( Give it a rating?)
The Sheridan Silver streak air rifle was made from 1949 up to the 1990's after that it became the Blue Streak.
The Blue Streak went into production in 1995 and is still produced.
It was made in 1975
There are 4 versions of the Blue Streak CB9 BLUE STREAK 1995 (SOLDERED VALVE) CB9 1995-1997 PHASE 1 CB9 1997-2003 PHASE 2 CB9 2003 - PRESENT BLUED BARREL CHECK YOUR SERIAL NUMBER AND SEE THE LINK BELOW Today Crosman owns both Sheridan and Benjamin air guns / rifles
There are 3 versions of the Sheridan Blue Streak. See the link below for the 2nd version. BTW today Crosman owns the Sheridan and Benjamin line of air guns. This link is from Crosman
Here is the link to all of the manuals for Sheridan and Benjamin. Crosman owns Sheridan and Benjamin See the link below.
Your rifle was made in 1977. It's one of two models, here is how to determine which one is yours. Measure your rifle barrel Model CB Blue streak barrel is 19.5 inches. Model CB9 Blue streak barrel is 19.38 inches 36.75 overall. It also has a Monte Carlo stock ( cheek rest).
by the serial number. Post the serial number here on answers, put it in the "air gun and air rifle" category and I'll locate an answer for you.