[Christopher]

I bought a second hand pair of HD25s and the left earpiece label looks exactly like the one in this picture:
 

 
 
 
Mine seem to be the HD25-1 Mark 1s; they have the right-angled cable with the flat connector pins going into the (delightful leatherette) earcups. The split headbands say "Made in Ireland".
 
However I've seen other variants of the HD25-1 which have two lines coming out of the "S" logo on either side:
 

 
And I've also come across these, sold by legit retailers, but with no Sennheiser logo whatsoever (!):
 

 
Which I've seen described as the HD25-1 II "Basic edition".
 
...And to round things out there's another image post on the TranceAddict forums which shows the model label as being HD25-1 II with no Senny logo, which also appear to be legit:
 

 
 (I'm aware there's 70 and 200 ohm variants of the HD25, I have the 70s.)
 
What's with all the different logo labels? It's so befuddling to those looking to purchase and they also introduce uncertainty when buying second hand.
 
The drivers in the Mk. 1 and Mk. 2 HD25-1 headsets are identical AIUI, aside from the rounded versus flat connectors (and velour earpads and carry case) are there any other material differences between the revisions?

 

[Christopher]

An update with more info about the entire range of HD25s, liberally quoted from a post by John Willett on DVForums:
 
 

There is no difference in the HD 25 headphones in the original version and the new Mk.II version - the difference is in the cable choice.
 
The current versions are:-
 

1. HD 25-1 II - 70 Ohms, 1.5m steel cable with rt.angled 3.5mm mini-jack and screw-on adaptor to 1/4" jack. These come with leatherette *and* velour earpads and a drawstring carry bag.
2. HD 25-1 II Special Edition - 70 Ohms, 1.5m cable with rt.angled 3.5mm mini-jack and screw-on adaptor to 1/4" jack. These come with only leatherette earpads and a nice zip case. These are no longer available as far as I am aware.
3. HD 25 II - 70 Ohms, 2m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.
4. HD 25-C II - 70 Ohms, 2/3m coiled copper cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.
5. HD 25-13 II - 600 Ohms, 3m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.
6. HD 25-SP II - Lower quality version without the split headband, 60 Ohms, 3m cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" jack.

 
This of course doesn't answer the matter of the differing side labels. I may try and contact John or Sennheiser UK by email but if there's anyone on here who's knowledgeable about the range, any input is appreciated.

 

[John Willett]

You have copied my list of HD 25 deviants correctly, so I shall not repeat it.
 
This is the official picture of the HD 25 on the Sennheiser Germany website.
 

 
The latest official picture shows no logo.
 
The logo with the wavy lines is the original Sennheiser logo - this changed to the version without the wavy lines about 20 years ago.  So both logos are correct.
 
The old logo did run for many years on some products until the tool needed changing.
 
I have no idea why they have now dropped the logo on the latest version.
 
I guess they are all genuine (ask Sennheiser) as I have never heard of counterfeit HD 25s.  But I stopped working for Sennheiser almost three years ago and am a little out of touch with the latest developments.
 
Though my own HD 25-1s are the originals "Made in Germany" that I bought in 1990 and are still going strong.

 

[Christopher]

Very useful info John, thanks for posting. I have the variants with Made in Ireland on the headband so I presume they're about 5-7 years old?