They are worth what someone will pay for them...the 28g is probably worth a little more as there were less produced...it also depends on when they were made (do you know?)...they are not necessarily a "matched" pair (serial #'s aren't even close...guessing they were not made the same year)...that being said they are very nice and the vent rib guns from the early 80's are desirable...but not really "highly collectable"...my book's show them between $700 and $1000...if you find the right guy you might get $2k for the pair, but I doubt it...I have 20g that matches those two NIB...I paid $425 for it 2 or 3 years ago at a gun show...it's serial # is close to the 28g you have...it's all timing. Very nice though...I'd love to have the 28g if you are considering selling them I might consider buying the pair from you...message me if interested.