Slavia
Which model of Slavia is it that you have? If you got it when you were 8, I'm guessing it is one of the junior size ones, so either a 618,622,624 or the slightly newer 625? The 620 is the larger model. None of them apart from the newer 630,631 and 634 will be worth an awful lot. The older ones mentioned above tend to go for anything from about £30-£50 including post depending on condition.(as once broken down, post is pretty cheap on the lightweight junior models) If your not in desperate need of the money, the guns probably worth more to yourself than the money.
Best Regards
Danny
CZ 200T/200 S Hunter/200 S Green/Slavia ZVP/612/614/615/618/620/622/624/625/627/630/631/634/ZVS Perun 734/CZ236-1/Tex3/86/Brno ZII/ZV3/ZV4/VZ47/APP661/Relum/Mars 618/Stella 518/Predom 188/170/Yunker 1/2/Lov21/Baikal IJ22/IJ38/Vostok/IZH61/IZH53M/MP512M/MP654K/MP661K