I agree, offer 100$. Badly beaten second hand anvils are insane nowdays. You probably wont readily find another.. and that one is badly beaten.
Aside from its broken heel, its face has substantial dents and pitting. It will do fine for heating & beating rebar artwork but to make nice forgings will be a challange.
Anyway, as far as it ringing. With its heel damage, it might not ring, or ring kind of a weird tone. What does not mean its bad, just damage like that can throw off its resonance ability.
But check if its decent rebound and hardplate is still firmly attached. ’Bounce’ a hammer all over its face. Any loose spots on its hardplate will easily feel and sound dead. Said that, dont be completely put off. If its loose near its damaged heel, Thats not unexpected plate to be loose right adjacent to the broken area.
Btw, I mention ’bounce’ a hammer, does not mean strike with appreciable force. Basically, at about 12-16” let a hammer drop, your hand is just to guide so it hits where you want and not let it fall when it rebounds naturally.