Some suggestions for kits as well as a wish list.

[ultravanillasmurf]

I suspect that the design of the 138 came first but that required reworking of the tank body/chassis and the availability of PAK40.

The 139 was probably put together as the 138 was taking too much time and they had a plentiful supply of tanks and Soviet guns.

I will have a look at my Panzer 38 (t) book to see what that says.

[ultravanillasmurf]

Is it me, but the models shown on the subject box have a distinct 139 look to them?

And, yes that is what Ripley said.

The PSC kit offered both the 139 and the 138 Ausf H.

[ultravanillasmurf]

This is a Military Modelling copy of the instructions/components from PSC
http://www.militarymodelling.com/news/article/pz-38t-and-marder-variants-in-15mm-scale/21173

[ripley]

Getting back on track for ideas for a wish list - how about Rubicon work on the 234 Armored Car series . They already have the late version  20mm turret as an add on kit for 250 / 251 , they also have both the short and long 75mm guns as well . These would , with a few extra bits , work to make  the 234/1  /3 & /4.  I think it  would make a nice 3 in 1 kit  And I still think a Berge Panther kit  would be winner . Going to build one myself , one day , still gathering bits and pieces 

[Jaeger]

Those PSC instructions are for the 1/100 scale vehicles.

[ripley]

IRC it's thought BA has some up scaled PSC kits in their collection