it sadly doesn't cover the image circle I need and it appears to use mixed materials.
Knowing you can but the TE-Q1/V1 19mm lens for about 300€ makes me wonder if there is a noticeable difference in quality - maybe the athermalization?
As it is from Ophir no need to be concerned about quality or materials and this is one of their higher spec lenses anyway. As Fraser says there are good reasons for using a material mix, and in this case it seems athermalisation and/or colour correction, as much as there can be for cost / cheapskating reasons.
The only oddity is the field of view quoted on 1024x768@12µm (36.3°) is wider than the lens mechanics allows (29.4°), so it would have slight vignetting (illumination loss at corners) if used for that arrangement.
Anyone looking to use it elsewhere, note the BWD on the drawing of 9mm, not the 'back focal length' of 11.51mm given in text
Bill