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.
On the right side in front of the trigger
It was made in 1974.
The serial number is on the left side of the loading port, in front of the model number. It may be under the black piece of rubber plastic.
It's usually on the left side of the barrel just below the loading port.
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.
The first Sheridan model C Silver Streak was called "The Sheridan" it was made from 1949 to 1990. After that it was called the C9 Silver Streak.
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.
It's very hard to date a Sheridan rifle. Let me explain. Sheridan started in 1945 and produced single shot air rifles. In 1977 Benjamin air rifle bought Sheridan and continued the line. In 1992 Crosman bought Benjamin. And again kept both names in manufacture. They decided to use Sheridan on the 20 caliber rifles and Benjamin on the .177 and .22 caliber rifles and air guns. At one point you could find both names on the rifles. In 1995 they came out with the C9 Silver streak model which later added the CB9 Blue streak model. there have been 4 different variations of the Blue streak. It's still made today. Crosman made some changes with their serial numbering system and I can't pinpoint your date of manufacture. See the links below
Sheridan has somewhat of a murky past. The company started in 1945. The silver streak was made from 1949-1990. In 1972 Sheridan started serializing their air rifles, starting with #000000. in 1977 Benjamin air gun company bought out Sheridan. in 1992 Crosman bought out Benjamin. Today Crosman owns all three companies. So if your air rifles has a serial number, it was made after 1977. I found a list of serial numbers for Sheridan on the Crosman web site but they only go up to (#437801) that were made in 1985. So yours was made sometime after 1985.
I'm not quite sure what you mean by BLOW BACK. The silver streak is not designed to "BLOW BACK" If it is then you may have a bad seal and it needs to be repaired. I suggest you contact Crosman ( they own Sheridan) Crosman has a home page and contact number at the bottom.
The Blue Streak went into production in 1995 and is still produced.