Weighting this sort of devices in the kitchen is as you say an issue of trust. On the other hand I have not been able to find a second source for the weight of this lens on LTM thread, beyond the one provide by Klomp and your kitchen.
Thus for example, the Rugfit M42 thread built in version is described as weighting 380 grams. and this is comfirmed by other sources too, but for M42 threads only. All this means that the buyer of the Jupiter will have to take care his version is LTM.
Now I have chequed the Voightklander version and here there are two different options: there is the Apo Lanthar 90mm, f3,5 (!) weighting 290 grams (which is not that far from the kitchen/Klomp version in terms of weight, but it will be of interest to know its size, since the Jupiter is also quite bulky.
But the second Voightlander option is quite seducing: The Color Heliar 75mm, very much acclaimed, with an aperture of f2,5 and a weight of 250 grams only. The size is strongly smaller too. Here the advantages become obvious. The lens is at sale for $329 and the buyer will have to add the adapter ($59) both for the Heliar as for the Jupiter.
If the buyer is able to buy its Jupiter 9 by physically going to see what he buys, and is presented with an acceptable for him mechanical version, then he could bring his adapter in his pocket - since he will need it in any case - along his M9 with film inside, ask the shop to allow him to run a few frames, rush to a 1 hour laboratory for a big enlargement and then have his judgement about the optical status too (remembering that lenses are to be judged at widest aperture and minimal distance.
Otherwise, Yanidel, you are sending him to the Soviet side of eBay, which you know is a landmine. There are jewels, no doubt, but great disappointments too.
US Fedka.com is a consistent seller of great lenses only, and great optics is his strongest side, rather than cameras. But the difference between his price for a good Jupiter 9 and the price of the Heliar 75, opens a wide field for thought.
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Finally, let me warn you, Aykut, that exceptional technically nice pictures above portrayed and further to portray, hide much more than reveal in the same spirit of the 10 bucks Yashica. The submitters have not detailed the mechanical status of their lens,
-nor if they have corrected or sent to correct their optics
-nor you see here the unlucky folks with stiff Jupiters
-nor the posters are revealing if the have been using tripods
-nor the f/stop number they used (a critical data)
-nor the film
-nor the scanner
-nor if they have used photoshop
-nor how many Jupiter 9 have their purchased until they found their Jewel.
-Finally, images with appealing subjects instead of boring subjects, confuse more than help. Add to this that no detailed data is attached and what you get is a classical abuse of a technical thread to personal picture gallery.
By implication you are requested to get astonished. By analysis keep your distance from these kinds of posts.
Cheers,
Ruben