Index & Format Inspection Methodology

The Atelier Index combines archival workshop documentation with quantitative UK secondary-market price tracking across ten luxury leather-goods houses.

1. How We Calculate 90-Day UK Resale Medians

Asking prices on peer-to-peer marketplaces frequently skew 18% to 30% above actual clearing values. To avoid inflated benchmarks, The Atelier Index tracks completed sales and verified consignment clearing prices denominated in Pounds Sterling (£ GBP) across the United Kingdom over a rolling 90-day window.

• Currency & Tax Normalisation: All prices are normalised to UK landed buyer cost in £ GBP, accounting for UK VAT and import duties where European stock is shipped into Great Britain.
• Outlier Trimming: We trim the top 5% (exotic/bespoke hardware outliers) and bottom 10% (damaged/parts-only and unauthenticated bait listings) before computing the 90-day median.
• Condition Grading Bands:
  • Pristine (Box Fresh): Uncarried or carried once, unmarked corners, protective film intact or zero hairline hardware wear, accompanied by full boutique set (box, dustbag, receipt/card/NFC verification).
  • Excellent: Gently carried with crisp structure, clean interior lining, intact glazing, and only faint surface micro-scratches on hardware feet or turnlock.
  • Good: Honest regular wear, softened corners, visible honey patina on vachetta or light corner rubbing, priced for daily wear or spa restoration.

2. How Our Serial, Date-Code & Blind-Stamp Format Inspector Works

Our deterministic rule engine checks three structural dimensions of an interior stamp:

1. Syntactic Pattern & Length: Checks whether the digit/letter count matches the designer brand's era grammar (e.g. 6/7/8 digits vs 8-character alphanumeric for Chanel; LLNNNN for 1990–2021 Louis Vuitton).
2. Workshop & Calendar Bounds: Cross-references factory prefixes against known workshops (such as 66 Louis Vuitton factory codes or Prada's Italian factory numbers) and ensures week numbers (01–53) and month numbers (01–12) are calendar-valid.
3. Era Cutoff Enforcement: Immediately flags anachronistic stamps, such as physical Louis Vuitton date tabs claiming dates after 1 March 2021 or numeric Chanel hologram stickers starting with series 32xxxxxx or higher.

3. Mandatory Non-Authentication, Superfake & Zero-Liability Notice

• Format Match ≠ Authentic Bag (Superfakes & Cloned Codes Slip Through): High-grade counterfeits (“superfakes”) routinely copy and clone genuine serial numbers, date codes, and blind stamps from real bags. While our database blacklists widely circulated cloned sequences (such as Mulberry 026904 or Chanel 10239481), a matching code format only means the sequence fits historical production records; a counterfeit bag carrying a cloned sequence can and will pass a code-only check.
• Zero Liability / Informational Benchmark Only: The Atelier Index (Carly Litwin trading as The Atelier Index) is an independent editorial archive and statistical price index. We never physically inspect handbags, never issue certificates of authenticity, and accept zero liability or financial responsibility for any purchase, sale, authentication dispute, or loss on third-party marketplaces (eBay, Vinted, Vestiaire Collective, auction houses, or private sales).
• Pro-Authenticity & Brand Integrity Stance: The Atelier Index is strictly pro-authenticity and anti-counterfeit: our tool exists to help collectors spot obvious factory/date mismatches early and to steer buyers toward authorised boutiques and physical multi-point authentication before any funds change hands.
• Strict Trademark & Non-Affiliation Notice: Strict Trademark & Non-Affiliation Notice (UK Nominative Fair Dealing): The Atelier Index is an independent editorial publication operating under UK nominative fair-dealing principles and is NOT affiliated with, endorsed by, authorised by, or sponsored by Hermès, Chanel, Louis Vuitton (LVMH), Mulberry, Gucci (Kering), Christian Dior, Céline, Bottega Veneta, Prada, Saint Laurent, Balenciaga, Fendi, or any of their parent groups (including LVMH, Kering, or Richemont). All trademarks, brand names, and model names belong strictly to their respective owners and are referenced solely for informational archive and secondary-market price reporting.