90/4 Elmar - the same?

I am fairly certain they are the same but just wanted confirmation.

I've owned the M-mount one for a few years now and love it for portraits and such. Slow, yes, but a great signature and I got it so cheaply. After acquiring and really enjoying using a IIIa last year I decided to watch for a LTM version. Found the one on the left recently, again for a very nice price and having been CLA'd by Sherry decided to grab it. Just shot the first roll on some Eastman XX and so far looks great.

Being such different looking lenses and made so far apart I just wanted to confirm some of what I've read online: other than a 3-element version made for a very short time, all 90/4 Elmars, LTM or M-mount, are identical in formula? Comment?

AFIK all 90mm Elmars are Tessar types.

Yes, as far as I am aware. Only the later lens will have more advanced coating and show less wear on the barrel and the focussing helicoid.
I am not a fan of collapsible lenses so would prefer the one on the left. I had a M3 with a collapsible Summicron few years ago and had the opportunity to try a rigid version for a few days. The feel of the rigid one was better and did give a minor improvement in performance

The optical block of the ltm version is located in the front and can be unscrewed to be used on visioflex.
Diaphragm location for 90/4 is after the second element, while in the 50/3,5 is after the first element. I dont know where is located in the M version but probably is identical to the ltm version and as E. von Hoegh wrote, they are closer to Tessar type.
I have the chromed ltm version and I like it a lot.

I have my 90/4 ltm but have to use it on my Canon IIIa, but soon my Leica III-A will be here soon. Don't expect much difference but we'll see. It'll be my first Leica.

Red Robin said:

I have my 90/4 ltm but have to use it on my Canon IIIa, but soon my Leica III-A will be here soon. Don't expect much difference but we'll see. It'll be my first Leica.

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Congrats!!

I love my IIIa.

Thanks everyone who replied. Appreciate it.