PartsBox does not assign serial numbers from a counter. A serial number in PartsBox is a single-unit lot: when you build, every device produced becomes its own lot of quantity one, identified by a unique ID Anything™ code. That code is the serial number. This is a deliberate design choice, and it is worth explaining why.
Start with the question that actually matters: what do you plan to do with a device after you have given it a serial number? If you stick a number on a board and ship it, never to think about it again, any numbering scheme will do — PartsBox will not know anything about that board once it leaves the building, and neither will you. But if you want to track a device individually — its inventory status, its test results, its repairs, the exact parts that went into it — then the only realistic approach is to create one lot for each device. Lots are the fundamental unit of stock in PartsBox, and they are what lets you attach data to a specific physical thing.
This is why serialization requires lot control. A serial number assigned without lot control is a half-measure. Even if PartsBox printed a neat sequential number for you, it would have no way of knowing that serial 1025022 was shipped to a customer last week, or came back for repair, or which reel of capacitors went into it. The number would be decoration. The lot is the thing that carries meaning.
When you build a project, turn on "Track each resulting sub-assembly separately?" in the build information. Instead of producing a single anonymous batch of stock, PartsBox generates a lot of size one for every unit built. Each lot has its own ID Anything™ code from the moment the build starts.
For a multi-stage build, those lots exist as soon as you begin. This is how a lot of medical-device and aerospace manufacturers work: they start the build with a first stage that places no components at all, used purely for documentation. Their inventory then already contains a lot for every device being manufactured, each with status "In Production". You can print labels, set custom fields, tag units, and record what happens to each one as it moves through assembly. When the build finishes, the status changes and the stock becomes available.
The serial number is the lot's ID Anything™ code. Take that code, or the first few characters of it, print it as a QR code or barcode, and put it on the device. Scanning it later brings up the lot: the build it came from, the parts and supplier lots consumed, the test data and service history attached over the device's life. You can serialize bare boards before assembly even begins, because the lots and their codes exist before a single component is placed.
Because each device is a lot, you can attach files to it. Store a test report, photos of an inspection, a rework protocol, a repair record, or a regulatory filing as a PDF or image, and it stays with that one device for its whole life. The paperwork for a unit lives with the unit, and you reach it by scanning the same code.
Legacy systems hand out sequential integer serial numbers from a central counter. People expect this, and PartsBox does assign an integer serial within each build for convenience. But as the permanent identity of a device, a sequential number has real problems that an opaque, globally unique ID avoids.
A sequential number leaks information. Serial 4,217 tells anyone who sees it roughly how many units you have made, and two units bought a month apart reveal your production rate. An ID Anything™ code discloses nothing — not your volume, not your pace.
A sequential number needs a single authority to issue the next value. That is a coordination problem the moment you build at more than one location, or build offline. An ID Anything™ code is generated locally, with no connection to any central register, and is still unique everywhere.
A sequential number is fragile. Restore a database from a backup, or have someone reset the counter, and you get duplicates — two different devices wearing the same serial, with no way to tell them apart. ID Anything™ codes are unique by construction, so a restore or a mistake cannot collide them.
None of this stops you from using a human-friendly serial number when you need one. Customers often require a specific format — a product prefix and an incrementing number, or an encoded date. Generate it however the customer wants and attach it to the lot as its name or a custom field. The lot's ID Anything™ code remains the unique anchor that guarantees traceability; the number you print for the customer can be whatever they ask for.
The honest trade-off is that an ID Anything™ code is not pretty and is not what most people picture when they hear "serial number". In exchange you get an identifier that is unique, opaque, generated anywhere without coordination, and impossible to collide — backed by a lot that actually knows what your device is made of and what has happened to it.
Lot control and serial numbers are on the Control plan.