Here are photos of the rare,  Pre1964 Hunter’s Friend Combination Set.
The photos describe the differences between the two sets, particularly the handles 
and the sheath designs of all known models variations.
Circa 1963,  Puma added a lanyard hole to the 6388. Additionally, the handles
were made with substantially thicker Sambar Stag.
The sheath was also reinforced with rivets and additional leather with stitching was added.
Lastly,  in 1974, the last year is known for the set to be produced, the leather sheath was made with
tan leather and sported the sheath keeper leather thong seen on other models.  This feature kept the knife from loss while being carried in the sheath. If you study the accompanying photos, you will see these features between the sets.