I think, for reverse engineering, that buying the marker and physically sectioning it to gain acess ot the internals would yield great results... This is what we do at work for failure analysis and test analysis of various parts.
However this will only youw know the dimensions of ONE marker that (hopefully) passed QC checks. To really reverse engineer soemthing without any intuition you need to analyze a number of identical parts to really learn some of the tolerence issues. However, with a sound engineering/analysis background, the design can simply be understood as to what tolerences it might require.
I'm hot like lava; you got a problem? I got a problem solver; and his name is revolver.
It's like a deadly game of freeze-tag; I touch you with a 44 mag, and you're frozen inside a body bag