[HomeBrew] Variac Transformer 100L

[R. Blackman]

Hello to group and a happy holiday season to all.

I have a very old boatanchor radio that I would like to bring up on a 
borrowed variac transformer.
I have no experience with variacs, this one is old and dusty, a web Google 
gave me little information on it.

Photos of the variac are here:
http://picasaweb.google.com/blackman.richard/Variac100L#

There are six connection points, some unlabeled. The 115 and 230 are 
obvious.

1)  is there a way to safely test this variac first without powering  it up?
And while on the 'powering up' subject:

2) can anyone give me some guidance on the connections so I don't blow 
things up 'real good'?

3) after properly connected, what is the proper procedure for use?
For example: how slowly do you raise the voltage?

Many thanks

Richard VA3NDO