Allerdings hat ein sehr geschätztes Forumsmitglied mir gestern noch geschrieben und recht gut argumentiert warum ich nicht zweifeln sollte.
"Dear Joel,
Thank you very much for your emails.
Firstly, please let me reassure you that we unconditionally guarantee the authenticity of the lagynos so we will of course take it back for a full refund if you wish, I appreciate how distressing it is if people cast doubt on an object.
I would however offer the following comments: I have around 30 years experience with ancient pottery, admittedly more in the Greek than Roman area, but I did not feel any reason to doubt the authenticity of the lagynos when I examined it. That said, everyone makes mistakes and I never pretend to be the exception or assume I'm always correct!
The forum comments which you raised as concerns are not necessarily accurate: the decoration on the lagynos is not hand-modelled, the whole vessel was cast in several separate moulds and then finished by hand. The lagynos with the identical spout/head is clearly from the same head-mould but there are variations in the way it is then finished before firing which is consistent with this technique - for example the incision decoration on the right hand-side of the hair on our example. This sort of parallel with minor variations is correct for this type of Late Roman pottery, and it should not to be confused with the similar North African slip wares which rely on creating a wheel-turned pot with mould-made appliques added afterwards to a plain body.
I actually tried to find the collection of the lagynos which you linked to when I originally researched our example and frustratingly I could not trace it though it appears to come from a museum somewhere and the fact that there is another lagynos using the same head-mould (but with hand-finished differences) in another collection is only a good sign as far as I understand it, and clearly they were produced in the same workshop/pottery factory. I'm not sure why a modern forger would go to the trouble of creating very different lagynos bodies but then same a little time by using the same head on the spout - if it was a terribly expensive object then possibly but at this level it would not make much commercial sense. The similarities and differences between mould-made lagynoi like this is actually what makes them quite interesting, just as one can find oil lamps using the same moulds but with slight variations also, and thus being able to attribute them to one particular maker or factory.
The other comment was on the surface/patina of the pottery: this was cleaned, probably when the vase was repaired but this does not raise suspicions to me if one looks at it in detail. Under the rather bright surface (probably slightly waxed by someone to bring out the colour as much as possible) one can see not only some accretions (which could be quite easily applied by a forger!) but also differential wear to the red slip coating over the pottery which has deteriorated and then flaked in places which would be very hard to forge successfully. Most copies of red slip ware are "aged" by rubbing away at the red slip to give it signs of age and the effect is not the same as gradual deterioration.
Of course this is only my opinion against others, and as I was the seller of the vase it would be obvious for me to defend it.
So, I can suggest a better and independent authentication if you wish: as it is made from fired pottery it is possible to conduct a thermoluminescence test to see when it was originally fired in a kiln. There is a laborartory in Oxford in the UK that can do this for around £250/300 but there are also others in the EU which might be easier to send it to. I could suggest that we arrange to send it to a laboratory of your choice (or one recommended on your forum) and I will pay for the cost of the test. If it confirms the authenticity of the vase I would kindly ask that you refund the cost of the test to us, and of course if it concludes that the vase is a forgery you have lost nothing at all.
If you would simply prefer to return it then that's absolutely fine also, we want our clients to be 100% happy, I only wanted to give you all options and show that I do believe that the lagynos is genuine and can at least to try to explain that there is reasoning behind the opinion

I hope all this makes some sense and I look forward to hearing from you,
All best wishes,
Rolf"