I'm pretty confident that they cannot discern if the tubes were sourced from Ferlach or not, but what they can say is that those are not their proofmarks. Now if there is something coupled with the barrel making process and the preliminary proofing process, then yes they make that claim. Now they do have the ability to check the proofhouse number for 1902 and say yeah or nay. For 1902, I think that the mechanics in Weipert are the culprits. But what we would need to see is either the preliminary stamp of an E coupled with a script W or for Ferlach an E coupled with a F. Then there are the typical Liege marks.
Kind Regards,
Raimey
rse