On Mon, 9 Jun 2008 16:18:48 +0100, "N_Cook" wrote:

r are they? how do you tell ?
:Raised pips spot-welded? on otherwise silver plated rockers in switch rated
:15 amp , 250V.
:If platinum, are they wholly platinum or somehow coated on a more base metal
:for the main body of the pip.


Going back into the dim dark recesses of my memory (with a little refreshing
thrown in) I recall the use of platinum relay contacts was usually only
specified where high reliability and/or currents and the presence of arcing was
expected. It is rare to find pure platinum contacts and they usually have some
added element to harden them and make them more resistant to tarnishing, arc
formation and wear. Materials such as iridium, ruthenium, nickel, molybdenum or
osmium are used.

How do you tell whether they are platinum contacts or not? I don't know. It may
depend on the manufacturer and you have to take their word for it. On 3000 type
relays used in telephony platinum contacts were marked with a V notch at the end
of the spring.