A tretubi frame would certainly explain the crankset. However, a 26.2mm seat post does not pass my sanity check for double butted CrMo tubing, which would typically use a post in the 27.0 - 27.2mm range. A 26.2mm post is typical of plain gauge, lightweight, hi-tensile steel. At the time, European tubing manufacturers typically used a single butted seat tube on their double butted tubesets and the only way to get close to 26.2mm post would be to install the seat tube upside down, with the butt at the top. Either that or Falck was an exception, having a tubeset with a double butted seat tube.