# C212 — The fixed SP 17-fold center crosses the 13-fold centers

23 September 2026 · Step 7 of 60, continuing C205.

Keep the sourced SP 17-fold interval fixed and compare its center with each of the three 13-fold centers. Its signed offsets are +190, −109 and −434.

| Chain | Fixed SP 17-fold center | 17-center minus successive 13-centers |
|---|---|---|
| 3 | -1581/2 | [Fraction(190, 1), Fraction(-109, 1), Fraction(-434, 1)] |
| 5 | -1577/2 | [Fraction(190, 1), Fraction(-109, 1), Fraction(-434, 1)] |

The familiar 190 separation belongs to the initial 6877 interval. It is not an invariant separation from every expanded 13-fold interval. The later sign reversal simply means the moving interval center has passed the fixed SP 17-fold center; no new event or reversal of historical order follows.

## Evidence and scope

K=529 and r=25/23. BC base B means (B+1)t/Bn BC; reflected AD base A means AD At/(A+1)n. Their civil span is B+A in both seasonal components, with no year zero. Signed paired centers are −B and +A; the center model uses components ±1/4 and restores this separation after dilation. An interval center is geometry, not an event or a proposed universal Mirror axis.

Regular Gears are restricted to Noah/Shem/Flood. Creation and Conquest retain fixed source-field members; no fourth Gear is admitted. Generated coordinates, source-field membership and stored graph incidence are distinct. File_18/File_09 and the frozen C127 graph are unchanged. Earlier N01/N03 qualifications, the missing Shem join, closed primers and unestablished original Reports 11–25 remain unchanged. This packet selectively uses prior evidence; it does not rerun completed campaigns. Assertions and alternative placements are not independent historical witness counts.

**4 step-specific checks and 19 frozen-input checks passed.** Exact inputs, results and predecessor hashes are in the accompanying JSON records; calculation code is in the evidence archive. Source dependencies are identified in the body and frozen in `sources/`.