Part VII of the Rules for Submissions describes "Compatible Armorial Content" in eight subsections:
VII.1 - Period Charges
VII.2 -Period Armorial Elements
VII.3 - Period Artifacts
VII.4 - Period Flora and Fauna
VII.5 -Compatible Monsters
VII.6 - Compatible Armorial Elements
VII.7 - Armorial Element Requirements
VII.8 - Registered Armorial Elements
VII.1 - Period Charges reads "Ordinaries and other
charges used in period armory may be registered."
If a charge was used in armory prior to the year 1600, it may be used
in submissions unless it is offensive, or presumptuous. If its use cannot
be documented to before 1600, this rule does not apply: see VII.6. instead
VII.2 - Period Armorial Elements reads "Lines of
division, lines of partition, field treatments, and other elements used
in period armory may be registered."
This does not speak to charges per se ' but to things like "indented",
"barry", "per fess with a left step", and so on. As with VITA, if the element
was used in armory prior to the year 1600, it may be used in submissions.
If its use cannot be documented to before 1600, this rule does not apply:
see VII.6.
VII.3 - Period Artifacts reads "Artifacts that were
known in the period and domain of the Society may be registered in armory
provided they are depicted in their period forms."
This means that pens are depicted as quill pens, not fountain pens.
We use the medieval, not the modern form.
VII.4 - Period Flora and Fauna reads "Flora and fauna
that were known in the period and domain of the Society may be registered
in armory."
Breeds, specific species, and other variations on a period creature
or plant that were not developed or known prior to 1600 are generally not
usable. For example, spiders are usable as a charge, but the Black Widow
is specifically a New World species and was not recognized by that name
until post-period. Many breeds of dogs, such as the English Sheepdog, are
postperiod developments. Australian flora and fauna have been specifically
banned under this rule.
VII.5 - Compatible Monsters reads "Monsters compatible
with period armorial practice may be registered in armory."
The notes go on to say "Monsters described in period sources may
be used in the Society, even if they were not used in period heraldry.
New monsters may be formed for Society use on the analogy of period monsters,
so long as all components remain sufficiently identifiable in the compound
monster. For example, the Society has created the sea unicorn parallel
to the sea lion and sea horse." New composite monsters are difficult
to design because it can be hard to design, a creature that is identifiable
by its constituent parts. Tread this ground with care.
VII.6 - Compatible Armorial Elements reads "Any charge, line of division, line of partition, field treatment, or other armorial element that has been ruled compatible with period heraldic style may be registered in armory."
For example, "dovetailed" has been ruled to be compatible with period heraldic style under this rule. The "compass star" is an SCA invention that can only fit under this rule. This rule provides a place to allow charges or other armorial elements that are post-period, so long as you can persuade Laurel that this charge is compatible with period style.
V11.7- Armorial Element Requirements reads "Only
elements from the preceding categories that satisfy the following requirements
may be registered in armory:
a. Identification Requirement - Elements must
be recognizable solely from their appearance.
b. Reconstruction Requirement - Elements must be reconstructible in a recognizable form from a competent blazon."
That is, if you can't describe it using the standard vocabulary, or you can't figure out what it is from the picture, the first six subsections are irrelevant. A new charge may require a definition so that you know what you are recognizing or describing. For example, there is a device that bears an SCA invented charge called a cross of Samildanach. If you saw the picture, you might scratch your head a bit. If you were also provided the definition of this charge, being four menorahs arranged to form a cross, things make more sense. If such a simple definition does not suffice to clear up confusion, the charge is probably not usable.
VII.8 - Registered Armorial Elements reads "Once an armorial element has been registered to an individual or group, the College of Arms may permit that particular individual or group to register that element again, even if it is no longer permissible under the rules in effect at the time the later submission is made. This permission may be extended to close relatives of the submitter if the College of Arms deems it appropriate."
This is colloquially called the Grandfather clause. If a submitter has registered a charge or element that is no longer registerable, that submitter, or immediate family (or analogous relationship for groups) may register armory using this charge. For example, the " rivenstar" appears only in armory of the Barony of Rivenstar. Laurel has ruled that the charge is no longer compatible with period heraldic style. Thus, only Rivenstar may register armory containing this charge. A canton of Rivenstar would probably be permitted to use a rivenstar under this rule.
Note that this lesson defines broadly those charges that could conceivably have been used in period armory. Some charges are forbidden to all submitters (the swastika and the pentacle come immediately to mind), while others may only be used in certain circumstances (the laurel wreath, a crown, a pelican, etc.).
Try your hand at some exercises.
For each item in the following list, cite the rule under which the charge might be registerable. If no rules apply, note that point.
1. A hedgehog
2. A poison ivy vine
3. A three-legged cauldron
4. A straight-sided stockpot
5. A roundel
6. A koala bear
7. A Moorish hair brooch
8. A cross gammadion (swastika)
9. An orange
10. A rubber tire
11. A grenade
12. A matchlock pistol
13. A griffin
14. A lion-headed sea-sheep
15. A brown thrush
16. A ducal coronet
17. A laurel wreath
18. An English sheepdog
19. A rottweiler
20. A hydrogen atom