# C1591 — Explain the SP2100 gap by its source and place values

## Question

Can the change120→2100 be decomposed without choosing a restoration target?

## Sources

```json
[
  "lower_spine_map.json",
  "File52c §1.1"
]
```

## Opened utc

2026-09-29T14:54:39.431274+00:00

## Results

```json
{
  "rule": "I(10(100h+10t+u))-10(100h+10t+u)=990(u-h), for this three-digit nonzero-end core register",
  "rows": [
    {
      "MSS": "MT",
      "core": [
        3,
        4,
        3
      ],
      "inverse_minus_original": 0
    },
    {
      "MSS": "LXX",
      "core": [
        4,
        3,
        4
      ],
      "inverse_minus_original": 0
    },
    {
      "MSS": "SP",
      "core": [
        3,
        3,
        1
      ],
      "inverse_minus_original": -1980
    }
  ],
  "MT_SP_inverse_gap_components": [
    120,
    1980
  ]
}
```

## Finding

SP first and last core digits differ by2, producing a1980 contraction. The inverse MT–SP separation is therefore120+1980=2100 before any536 comparison is made.

## Reassessment

Use that already-derived separation with the common2700 stage shift and Shem600.

## Checks

```json
{}
```

## Closed utc

2026-09-29T14:54:39.431753+00:00

## Record provenance

Exact record hash: `202a66531a6e652eee3f555dd7f321228a5963c88784634e29ea7011f87397b8`

Source journal: `Research_Cycles/C1585_C1634/journal.json`