WD of this 9.3x NA 0.25 oil objective

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I just bought this 11x NA 0.25 LOMO oil objective 190TL:
http://www.ebay.com/itm/272533932307

I would like to know its precise working distance on 160TL, if anyone knows.

Its physical length is about 28mm. No WD spec on 190TL. On 160TL, WD would be longer and magnification would be lower (changed to around 9.26x).

I may be able to measure it on my 160TL microscope, though am not sure I can measure it precisely (I need to back up from touching cover slip to sharp focus, using and counting fine focus turns - that touching point may not be precise, since I don't want to crash the top lens into cover slip).

I need WD to calculate shim/spacer thickness to parfocalize it to 33mm. We need to cut an adjustable spacer (7mm-11mm) to around 4.7-5.0 mm. We have to cut a little more than necessary, then parfocalize it with super thin shim rings.

The question is how much to cut? WD will tell us that. I prefer cutting precision to be within range of +/- 1mm. I can shim/extend myself within 1mm cheaply and precisely. But we only want to cut once, since my machinist friend does not live in my city and does not have a microscope.

I have seen a crazy long working distance of 1.8mm, from water dipping objective (LOMO 40x NA 0.75).

This 30x NA 0.65 190TL LOMO seems to be of the same series: http://www.rafcamera.com/en/lomo-micros ... e3dee1c07d

I am not sure Raf's spec numbers are correct though. He said that WD is 0.40 mm and parfocal length is 20.75mm. I suspect that 20.75 mm is physical length, because my seller measured that 30x oil objective to be around 21 mm in length. Though with immersion objectives, pfd can be very close to physical length.

And as reference, here is Raf's spec for another 190TL oil pol objective 95x NA 1.25: http://www.rafcamera.com/en/lomo-micros ... at-95x1-25
WD = 0.06 mm, parfocal length 33mm. That Pfd sounds too long to me, judging from the photos.