That's very interesting. It sounds like an early one. As in pre-'56. If it is, you're in the money! You'll see the option to post photos below and to the left of the dialog box (as Attach Files) once you have ten posts here on the forum.
Here's an excerpt from a reference that I found. If you'll read through it, you may be able to figure out the years it was made in.
"(1949 - 1962). Sculpted front blade sight (1949 - 1963). Grooved receiver (1949 - 1967).
Pump Tube stamped 'SILVER STREAK' on left side. 1950 - One change. Slab sided stock discontinued. 1951 - Two changes.
Patridge rear sight introduced. (introduced late 1951). Hole on right side receiver (allows pin removal on Bolt) (1951–1956) 1952 - Three changes.
Blue Streak model introduced (May 1952). Forearm attached with roll pins. Pump tube now has 'MADE IN USA' stamped on right side after RACINE, WIS. 1953 - One change.
Knurled Windage knobs discontinued 1954 - No changes 1955 - One change. Crescent butt stock replaces straight butt stock.
1956 - Two changes. Rear sight now attached with set screw and two dimples, and is no longer soldered to barrel. (May 1956 - May 1961).
Hole on right side of receiver removed (Mid - Late 1956) 1957 - No changes 1958 - No changes 1959 - One change. Introduce lower comb on Stock. 1960 - Three changes. Trigger guard now wider and attached with Rivet and one screw.
Sheridan blue streak serial numbers age
(Aug 1960). Introduce new stamped lettering on pump tube '5 M/M CAL' now stamped on left side of Tube. Blue Streak models now have 'BLUE STREAK' stamped on the pump tube. 1961 - Three changes.
Introduce larger 'Beaver tail' style Forearm. Change from straight bolt to curved bolt handle with hole on ball-end and pinned to Bolt. (May 1961).
Sheridan Serial Number Identification
Rear Sight now attached with 2 set screws. (June 1961 - May 1971) 1962 - One change. Hand Guard introduced 1963 - One change.
Rocker Safety introduced. (Feb 1963) 1964 - Two changes. Inspection dates now stamped (backwards and alphabetically) on the left side of the receiver. (Jan 1964 - Apr 1972)."
Edit - Here's a pic of an early one. Does yours look like it?
View attachment 362343 Cheers,
J~