25-75 USD
Around $50
A model C .20 caliber not a model C9 or C9PB in very good condition is worth around $105 to $130. If you want the owners manual, see the link below. Download the C9 owners manual it will be almost the same as the "C" Crosman airguns owns both Sheridan and Benjamin airguns.
Around $100 in good condition.
The sheridan H series in good condition is roughly worth $100
The Sheridan Silver streak takes a 20 Caliber Pellet. You can find them at a good sporting good store or online (see the link below). Remember a heaver pellet will fly slower but it will fly straighter and have more "knock down power" than a fast light weight pellet that is more affected by crosswind.
You have given me all the information except the model. Sheridan has several different models at different prices
I assume that you are asking about the .20 cal Sheridan C Silver Streak NOT the C9 Silver streak. (It's worth more.) New in box: Excellent condition $185 Very Good $160 Good $120 This is just an estimate.
Sheridan C silver streak in good condition would be worth between $125 -$160 USD
I believe you are asking about a Sheridan .20 cal (5mm) air rifle. They started to make this rifle in 1949 and stopped in 1990 ( sheridan sliverstreak model ) During the 1990's the name changed to C9 sliverstreak and C9 bluestreak. The value is determined by the current condition of the rifle. You did not give any such information , therefor I can not answer you.
In order to give you an estimate of value. I need to know a few more details like, The model number. Sheridan made 5 different pellet guns and 7 different rifles. The 5 pellet models are E, EB, ED, HB and H20PB. Which one is yours? Is it still working? What condition is it in. Poor, Fair, Good, Very Good or Excellent (Like new) without this information No estimate of value can be given. In 1977 Benjamin airgun purchased Sheridan, In 1992 Crosman purchased Benjamin. Crosman owns Sheridan today. Sheridan and Benjamin look similar. All the .177 and .22 Caliber rifles are marked Benjamin. All the .20 caliber rifles are marked Sheridan. Other than caliber the two models are identical. If you want the owners manual for your pistol a link can be found on the Crosman home page.
This is for the Sliver Streak not the C9 silver streak. In good condition it is worth between $85- $105
It would be worth between $65 - $80