Henry_Best:
That's an unusual arrangement.
Usually the two arms are diametrically opposed, either vertically or horizontally, so that they can compress the work parts together before sending the current through them. I can't see how your welder would work without pinching the two work parts together.
See Web Hosting, Reseller Hosting & Domain Names from Heart Internet for an example.
You can see here the Spot welder opposed configuration
The series configuration spot welding is not very common, but always used for welding batteries.