That seems a bit high for a 712. I bought a beautiful Sunburst Orange 914 stock for $250. Absolutely stunning bike. I also had a Miyata 1000, an NOS Miyata light blue mid 90's track bike with chrome fork/stays and a fully lugged* Miyata Ridge Runner in the darker Miyata blue. Great bikes all. But for $350, hold off for a better Miyata. Patience is always rewarded.
*frame and fork