# C223 — The midpoint carrier 552→600 belongs to the same ladder

23 September 2026 · Step 18 of 60, continuing C205.

The Creation-to-midpoint widths are 7176=13×552 and 7800=13×600. Their carriers are simply the averages (529+575)/2 and (575+625)/2, and 552×25/23=600.

| Chain | Creation to sourced midpoint | Creation to generated midpoint |
|---|---|---|
| 3 | 7176 | 7800 |
| 5 | 7176 | 7800 |

This places the named first midpoint inside the same 529-centered framework. The number 600 arises here as an average carrier and does not acquire a Noah/Shem biographical role from that arithmetic alone. Its second midpoint endpoint remains generated, as established in C217.

## 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/`.