The loco in the picture is one of Brack's 3D printed 1:24 'Sipat' Bagnalls from Shapeways with some added details. See http://gn15.info/forum/viewtopic.php?f=1&t=9716
for the full story. The basic 3D print is a great little model that really captures the character of these little locos and is well worth the small extra effort to add the details that the 3D printing process cannot do.
I have not got around to making any track gauges for the Karlgarin code 125 rail yet. I am one of those smug wotsits with a lathe so I was going to turn some up, but I think it should be relatively simple to make a track gauge using a 25mm long M5 cheesehead bolt, some large washers and some nuts.
The first job is to thin two of the nuts so that they are a little thicker than the head of the rail, rail head plus about 0.1mm should do the trick. Place a washer against the bolt head and run one of the thinned nuts up against it, then tighten it to trap the washer. Add a second washer against the thinned nut, then run an unmodified nut up against the second washer. Add a third nut and run it along the bolt until it is at a bit less than track gauge from the second washer, then add another washer and a thinned nut. Next step is to adjust the third nut and the second thinned nut to set the track gauge over the outer face of the third washer and the face of the second washer closest to the bolt head. Add a fourth washer against the thinned nut and secure this with another nut. If you want to make sure nothing moves you could add a smear of epoxy to the bolt's threads as you build up the layers of washers and nuts, preferably not the rapid epoxy as you may run out of adjustment time. You could add extra washers and thinned nuts for the check rails, but bear in mind that the important dimension is that between the back of one wheel and the flange root on the opposite wheel. This is because the check rail has to restrain the back of the wheels to prevent their opposite wheels hitting the crossing (or frog if you must) nose and climbing over it. Much easier to build than explain, hope that is of some use.
I have yet to build any pointwork, but I think I may have to take a little off the foot of the check rails to give the correct flange way. I was thinking of using the intermediate standards as shown on the OO gauge association website which should suit the wheels that I am using under my stock - see http://doubleogauge.com/standards/commercialtrack.htm
. Just ignore the sleeper spacing