There are several significant differences between the original, no number, short box version and the second offering with the long box numbered CL-3. Both are Van Loo Chipmunk's (also the yellow label CL-3)
The original no number short box has two piece fuselage sides for both sides. Sig could not fit the one piece sides in the short box. Next; the ribs are very different from all proceeding versions. They resemble Nobler profiles (Jim Van Loo is on record as stating they are not Nobler copies, but are virtually the same) also the landing gear bolts to plywood ribs with U (or J) bolts. Again, all proceeding kits had blocks that are mounted inside the wing across a couple ribs (I think on the bottom spar too). The short box cowl, and wheel pants are slightly smaller. The short box is by far the rare one to find. It should be noted the plans are different too, reflecting the rib, & landing gear, differences. BTY Ty, you bought the short box kit from me many moons ago! Since then, I recently aquired the long box CL-3!
Anyone wanting to build a CL-3 Van Loo Chipmunk, but can't find a kit. The CL-19 Super Chipmunk is almost identical until you compare the cowl. Build the Super, carve the cowl!
Edit: The MAN plans (1968?) Show the first version with the different ribs, landing gear, cowl, and wheel pants.
If my recollection of the Van Loo Chip, history is correct, Jim's original contest winner was a foam wing.