Hi Phil. No I have never seen one before, been looking for the last 30 years! I have seen the adverts for these with the appropriate card target but I have never even seen the card target! I would love one for my collection. I think the card targets will be the same size as the later ones. My 1937? green coloured catalogue shows Horseshoe target sizes as 10 x10 1 inch and 6.5 x 6.5 x 1 inch, my Jan 1938 catalogue shows the now square holder at the same sizes.
Regards Paul