Here is Sennheiser's response to whether the E838 and E935 share the same capsule when I asked this question a couple of years ago :-

"Thank you for your enquiry with regards to the e840 & e935. These mics are very similar but the capsules are not the same. The e935 has a different shock-mount and is made to a higher tolerance to the capsule found in the e840. The e838 is now a discontinued microphone. The e935 has a lot better handling characteristics when compared directly with the e840. The capsules are of a higher tolerance and in effect this means that if you use more than one e935 then there is far more chance that the mics will sound identical. As far as frequency response and tone are concerned then the tone of an e935 is likely to be better than the e840.
Obviously sound is very subjective and the most important factor is to find a mic that best suits you vocally. This means that it will reproduce the sounds as you expect them to be or as you as an individual hear them."

I am going to borrow an E935 and do a thorough a/b over the next week or so.