Bert wrote
excuse me please for the late answer to Your question.
The most obvious visual differences between Hf.12 and Hf.14 are:
the chimney: Hf. 12 with a ring at the top and a conical form, Hf. 14 without that ring and a normal round form
the grip on the chimney for folding: Hf 12 joined up and down, Hf. 14 only up
the wheels: Hf. 12 with 12 bolts, Hf. 14 with six bolts
the carriage body of the Vorderwagen: Hf. 12 made out of wood, Hf. 14 made out of steel sheet.
the spring swank connection: Hf. 12 with holes, Hf. 14 without holes.
Thanks a lot for your anwer, Bert.
About the chimneys I can not see see difference. I see all chimneys cylindrical, not conical...
The differencies are so small that in the most of the images I can not differenciate between both models....
Regards Sturm78