Mettler H15 analytical scales issue

[ChristofferB]

Hi!

I recently aquired an 1962 vintage Mettler analytical balance in near perfect condition, the H15 model. It's a marvel of a swiss clockwork! it's basically and old fashioned scale with one 'pan' being constant and the other being adjusted by turning knobs that lifts and lowers different weighs BCD-style! the microgram scale is a tiny film scale on the beam of the scale projected onto the translucent front panel like a vernier. I'll put up some pictures at some point. To be fair, it's more mechanic than electrical, but I'm hoping there's someone here who's actually used/maintained one.

It measures the mass up to 160 grams, down to 4 decimal places.
Here's the problem: it measures wrongly! I weighed out an object (binder clip) on the modern Mettler scale in my lab, and then again on mine. It's consistently about 417 mg off on that mass.

Now, I haven't done a whole series of standard weighs and made a calibration curve yet, but my initial thought is that i know it has a means of tare-ing it, this works by adding a permanent weight on one end of the beam, and indeed there are little washer-like weighs there, but if it IS in fact calibrated properly, I don't want to mess with factory calib. which is probably better than I can do anyway.

What do you think? Anyone happen to have the manual for this? (or the H5 or H10, they're almost identical)

thanks for the look!

[ElektroQuark]

I have an H20T. The manual is for the H10t/H20T models.
I can  scan it if you want.

[ChristofferB]

That would be very very helpful! especially the parts about calibrating and tare-ing!

thanks!

[ElektroQuark]

I checked yesterday, it's in French and Spanish. Any preference?
There are a lot of images, so it could be helpful.

[ChristofferB]

Oh I'd much prefer french!

Thanks for the help!

[ElektroQuark]

I will scan it tomorrow at work.
Send a PM with your email, please.