hi,
In the rules it's written: "It is not possible to use the Laboratory Text from a lesser enchanted device to instill a power in a greater device, or vice versa, nor can any other magus make use of a Lab Text concerned with instilling an effect into a talisman." (emphasis mine)
Do that mean that the magus who made the talisman and instilled an effect in it can use that labtext to invest the effect into another invested item which is exactly the same shape & material than the talisman?
Nothing in the text seems to forbid it: talisman is an invested item, not a lesser item (so first rule is okay), and the magus itself is no "any other magus" and so is not blocked by the second part but I'm quite puzzled since I realized yesterday things I thought clear were not
I guess the magus can use it to create copies of his talisman. He would have benefited from an extra +5 to create the labtext so there is that.
Then again, typical labtexts of invested devices are sharable... Would the new lab text generated from the non-talisman activity differ from the original? I assume so as you do not have the intricacies that allowed the original +5. This, to me indicates you cannot use the talisman labtext to instill a non-talisman.
It is a very niche case use. I'd allow it with the requirement that you need to experiment.
You could research it and create a form of "Talisman of Hermes" minor merit where you can use others Talismans labtexts to invest your own.
Slightly off-topic, but I consider a spirit talisman created using inscriptions on the soul as sufficiently different from a normal talisman to ignore this rule. A human spirit is a human spirit is a human spirit - same size, shape, and composition. And it's using a mystery, so certain of hand waving is appropriate. If a bunch of Bjornaer with spirit talismans (because Clan Ilfetu has almost certainly learned how to initiate that mystery by now, it's too useful in heartbeast form) want to share lab texts, more power to them.