Part numbers and measurements that disagree across systems

One item, several identifiers

A single product usually has more than one legitimate name, each assigned by a different party for a different job.

• The manufacturer part number, assigned at design and revised with the product.
• The distributor SKU, assigned by each distributor to fit its own catalog and often reformatted from the manufacturer's.
• The GTIN or UPC on the package, which identifies a specific packaged unit, not the part in general.
• The ERP item code, assigned internally and rarely seen outside.
• Legacy and superseded numbers, still present in old quotes, service manuals and cross-reference sheets.

How identifiers drift

Most mismatches are not errors in a single place. They are transformations between places.

• Formatting: hyphens, spaces, leading zeros and case dropped or added when a number moves between systems.
• Prefixes and suffixes: a revision or a finish code carried in one system and truncated in another.
• Unit of measure: the same number identifying an each, a box or a pallet depending on the system.
• Supersession: a part replaced by another, with the replacement recorded in one catalog and absent in another.
• One-to-many: a single manufacturer part sold as several SKUs by a distributor, one per package or finish.

Measurements have more than one right answer

A dimension is not a number. It is a number, a unit and a basis, and the same product can truthfully carry different values on different bases.

• Nominal versus actual. A board sold as a two-by-four measures roughly one and a half by three and a half inches. Pipe sold by nominal size has an outside diameter that is a different number again.
• Unit size versus opening. A window or door has the size of the unit and the size of the opening it fits, which differ.
• Imperial versus metric, where one value is the conversion of the other, rounded differently in each place.
• Rated versus measured, and a tolerance that makes two slightly different numbers both conforming.

An illustrative record

The record below is invented to show structure. It is not data about any product or company.

item: Casement window unit, series ABC
manufacturer_part_number: ABC-3040-R2   (source: data sheet, rev 2, confirmed 2026-04-02 by engineering)
distributor_sku: D-ABC30R2             (source: distributor catalog export, 2026-09-18)
gtin: not assigned (sold as a configured unit)
unit_width: 36 in, basis: frame, tolerance: +/- 1/8 in
rough_opening_width: 36 1/2 in, basis: opening (source: installation guide, rev 2)
supersedes: ABC-3040-R1 (source: engineering change notice)
status: active

Why it matters when a machine reads it

A person reading a catalog infers which number is meant from context. A purchasing agent or an assistant comparing three suppliers has to decide whether two values are the same quantity. If one source gives the frame width and another the opening, the comparison treats a real difference as an error, or an error as a difference. Either way a buyer receives a wrong answer with the confidence of a precise one.

What governs it

The remedy is not to force one number everywhere. It is to record each identifier and each measurement with its kind, its basis, its source and its date, and to state the mapping between them: which SKU points to which part number, which dimension is on which basis, which part supersedes which. The manufacturer owns the engineering values and the part number. The distributor owns its SKU and the cross-reference to it. The record states that order, and a comparison against every copy shows where a system has drifted. See dealer network data governance.

Questions