ORIGINAL: w8ye
The later model Saitos (most of them now that don't have brass sleeves for cylinder walls) have aluminum seats. But the seats are chrome plated
The OS, Magnum, ASP, SC, etc are bronze
Yes, it is quite clear. Disadvantages with the valve seat of aluminum with chromium, it can not be repaired and will be ruined of lapping. As long as the compression is good, it's best to let the valve seats in Saito in peace and remove carbon with great care.
Merry Christmas and Happy new year to all folks!