On Wed, 11 Nov 2009 23:41:36 -0800, Sparky wrote:

This cap was removed from a 70's-80's German industrial machine:

http://i37.tinypic.com/10psxg3.jpg

It has no polarity markings. One terminal is common with the metal case. Is
this always an indication of the (-) terminal?

The base has molded terminal locations numbered 1-4, two of which are empty:

http://i36.tinypic.com/e6x542.jpg

Me, I'd guess the terminal marked with the '-' is negative, but that's
just my warped thinking.