The Retlas was loosely based upon the Gardner size 1 vertical gas engine.
I just confused myself by looking at the Gardner "O" drawings.
The bits that we are missing on our Retlas drawings are the sheets with the cylinder/liner, valve chests and the valves on it: are they the same as on the Gardner size 1 engine
Looking at the page numbers on our drawings, assuming that all the drawings are sequential, the ones missing are: 201, 202, 205, 206, 208, 209, 211 & 212
I was going to redraw it in Alibre (Cubify) but with a few sheets missing it is not as simple as it could have been.
Jo