I have a PC 690 with the fixed and plunge bases. I bought them before I was ready to use them because I got a good price at Sears. The plunge base has not been used and has been in the case since I bought it except when I took it out to see that it worked. I have used the fixed base once or twice. Last night I took the plunge base out of the case planning to use it today. The inside of the base had what seemed to be several black specks on the surface. When I tried to clean the base I discovered that they were pits. Some are fairly deep and about the size of a pencil lead. The fixed base is not pitted but shows some discoloration. I think these bases are cast and maybe what I'm seeing are casting flaws. I've e-mailed PC but it will be next week before they reply. If anyone of you have had a similar problem or an idea of what is the cause of the pitting I will appreciate your input. TIA