Source: https://guthlabs.ai/docs/instruments/currency-converter-offline-snapshot/implementation/

instrument implementation / implementation-contract

# Currency Converter (Offline Snapshot) implementation

A source-bound implementation contract for Currency Converter (Offline Snapshot); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-047

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification does not provide the bundled currency-rate table, its date, supported currency codes, missing-rate behavior, or sign convention. Consequently, ordinary cross-currency conversions cannot be numerically verified from this specification, and unsupported currencies can produce undefined lookup results unless explicitly rejected.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "amount": 1,
    "from_currency": "EUR",
    "to_currency": "DEM",
    "snapshot_date": "2025-01-15"
  },
  "expected_outputs": {
    "converted_amount": 1.95583,
    "notice": "Rates as of 2025-01-15; may be stale."
  },
  "reference_data": {
    "rate_rows": [
      {
        "currency": "EUR",
        "units_per_EUR": 1,
        "source_convention": "European Commission/ECB irrevocable euro conversion-rate table"
      },
      {
        "currency": "DEM",
        "units_per_EUR": 1.95583,
        "source_convention": "European Commission/ECB irrevocable euro conversion-rate table"
      }
    ],
    "quote_convention": "units of currency per 1 EUR"
  },
  "working": "EUR rate = 1.00000 units/EUR. DEM rate = 1.95583 units/EUR. Converted amount = 1 EUR × (1.95583 / 1.00000) = 1.95583 DEM. This lands exactly on the official fixed EUR-to-German-mark conversion entry."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/currency-converter-offline-snapshot/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/currency-converter-offline-snapshot/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/currency-converter-offline-snapshot/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`