A Wizard's Sigil is a unique identifier of each magus. Thus in theory once you know the casting sigil of a spell you can identify the magus who cast said spell.
There is an issue though. If you want to identify a magus by knowing their sigil you have to also know what magus has what sigil. How easy is it to find out what sigil belongs to what magus?
Do tribunals keep records of the current and/or former resident magi with information about their sigils? what about their voting sigils, lineage etc? Would you allow such information to be covered by Organization lore(Order of Hermes)?
Assuming that there is no centralized tribunal record, what other options are there? spreading the word that you are looking for a magus with X casting sigil?
How easy are sigils to identify? According to the core book it seems like a casting sigil is easily identifiable once you know that to look for, i.e. all magi are able to identify sigils that they witness themselves. However not all the example manifestations of a casting sigil seem to be created equally identifiably. (one in the core book is a motif of a flame and another is orderliness).
I am asking for personal opinions and experiences just as much as for references to specific rules.
HoH:TL p.71 Spell Traces and Sigils: "As well as giving a unique quirk to the spell's operation, the wizard's sigil gives a unique signature to a spell trace. When investigated by an approriate Intellego Vim spell, this unque mark is revealed. <snip> In order to recognize a previously encountered sigil, the Quaesitor should make a Perception + Awareness roll with a difficulty set by the storyguide. (italics mine)"
So it would be an Intelligence + Tribunal Lore roll to know, which magus' spells have that unique quirk. A Quaesitor who checked an illegal spell for its unique signature with HoH:TL p.75 Impression of the Faded Sigil or Sight of the Sigil could often derive the likely suspect.
But beware of casters with ArM5 p.159 Shroud Magic and not from the Tribunal: then a real magical-forensic investigation might be in order, involving not only gathering of traces but also the full procedure of the Tribunal in session requesting Quaesitores to verify and endorse a suspect's testimony (HoH:TL p.64ff).
To me, the above statement implies that there is some form of common ledger, either in the form of an actual document containing the information about sigils, or perhaps more likely that the quaesitors have the names and sigils (plus presumably other information) memorized in order to help them in investigating.
The reason why I conclude so, based on your post is that since you would allow a "Tribunal lore" roll it stand to reason hat there exists a knowledge about the the tribunal, including information about the magi resident in the tribunal, that can be studied and called upon by those inclined to study such Tribunal lore.
It is not entirely clear to me if you are referencing a canoncial rule or a house rule when you allow for rolls against Tribunal lore to identify sigils.
EDIT: Sorry for the lack of clarity I meant: It is not entirely clear to me if you are referencing a canoncial rule or a house rule when you allow for rolls against Tribunal lore to identify magi by their sigils.
Just 'common sense'.
There are not too many magi in each Tribunal: if the respective unique quirks of their spellcasting were not known, very little would be known about them at all. In general, there is a Quaesitor present when an apprentice is made a magus and given her sigil - and typically this involves spellcasting by the apprentice to show her ability. Whether this Quaesitor then marks the unique quirk of the maga's spells into a ledger, informs his sodales - especially the other Quaesitores - by word of mouth, or just recalls it for the next decades - like an old-style commissioner or beat cop connects a way of robbng a bank or breaking a safe to an old 'customer' of his, might be specific to saga and Tribunal, though.
Your point about the quaesitor being present at the gauntlet of new apprentices makes a lot of sense and I agree with it. Likewise about how knowing the sigil of a magus is kind of a low bar for knowing about them.
I would argue, like you do, that the exact form of how such knowledge is preserved matters less than the fact that the knowledge is preserved. I would term such preservation a "ledger" regardless of the form taken.
I mean to ask also about what is the personal opinion and that of others. How are such "ledgers" kept and to whom are they accessible. There is after all a pretty big difference between having a publicly available register of all the magi in the tribunal and their sigils and having the knowledge memorized by the collective corpus of quaesitors in the tribunal, possibly not shared with outsiders.
Even without a ledger, someone's sigil is information that is likely known about them in social conversations (aka gossip) unless they take extraordinary measures not to reveal it (like never casting in front of other people)
We also have Casting Tablets, which meld the Wizard's Sigil of the tablet's author with that of the caster, IIRC.
How do people handle the traces of spells cast with the benefit of a Wizard's Communion of whatever duration?
also keep in mind that another's sigil could be mimicked. Whether it would require finesse or for the spell to be affected with MuVi or for the spell to be designed with extra sigils (or if multiple options exist) may be saga dependent, but adding a scent of roses to an otherwise standard spell (for example) should not de overly difficult.
You raise a very interesting point. I had always thought that sigils would be either "deleted" or changed with a MuVi effect to directly transform the sigil trace into the sigil of another. You are essentially suggesting a third way by adding something that corresponds with a specific known sigil. That is very clever.
That is the situation, where Quaesitores with HoH:TL p. 71 Acute Senses Mastery, good Perception and Penetration shine. It is pretty hard to beat them with MuVi spells removing, masking or faking sigils.
Yes, and luckily. It would be a very poor situation for the quaesitores if they could not investigate better than other magi
I assume the hope in masking a sigil is that either the non-quasitores doing the initial investigation will fail to find the traces and thus not report anything to a quaesitor or that it will take them so long that the traces have decayed so much that even whatever quaesitor eventually shows up to investigate will not be able to glean anything.
or 1) hoping you get an inexperienced Quaesitores who will follow the false trail 2) just making the investigation more difficult, 3) laying an argument for defense based on an alternate theory of the crime or 4) belief that you in fact are better than the quaesitores, after all, nobody hears about the magi who get away...