The registration crosses on mine are a newish addition.. i tried them out a couple of years back and didnt get good feedback as restorers didnt want a cross, even if its under the siderail.
Ive put them back in as in all honesty, better results are achieved by having them.. it makes life a lot easier for the end user and seeing as the stencil is an opaque yellow, it gives the user confidence that once the last colour is removed it will all align correctly.
Before the registration crosses, the last colour was an act of faith.

Jeffs product used to be either the blue or grey stencil mask.. its very high tack and often lifts paint when removed. This type of mask is ONLY to be used if the repaint is done with household acrylics.. even then, theres no guarantee it wont lift paint.
The light blue version is very low tack and is only to be used for acrylic lacquers etc.

The yellow is from a different manufacturer.. comes in yellow or white and has a different adhesive.. its a porous vinyl that acts to prevent leeching... by far a better product but you lose the semi transparency of the blue or grey... hence the now standard registration crosses on my stencils.
Clear application tape also.. no more using the paper stuff which they used to.

So, on the surface, it appears we are using the same product... wether Classic A is using the yellow because they cant get hold of the cheaper blue/grey we'll wait and see.
But the stencils you have are a better product than the Ebay listed pictures where the stencils are hung over a window so you can see the shapes... this is blue/grey mask with a paper application tape.

http://www.ebay.com.au/itm/Williams-HIGH-SPEED-Pinball-Machine-Stencil-Kit-/230924815305?pt=LH_DefaultDomain_0&hash=item35c4310bc9