A Longines reference number has five blocks, and each describes one thing: family, model, case material, dial, and bracelet or strap. In L3.781.4.56.6, L3 is the family, 781 is the model, 4 means a steel case, 56 is the dial and the final 6 means a steel bracelet. It is one of the clearest systems in watchmaking.
Longines makes a very wide range, and many watches share a name: there are dozens of HydroConquest and Master Collection models. The reference tells them apart. We have 2,147 Longines watches in stock, each with its reference under the title.
How to read a Longines reference number
| Block | Example | What it tells you |
|---|---|---|
| 1 | L3 | The family of watches |
| 2 | 781 | The model: case size and movement |
| 3 | 4 | Case material |
| 4 | 56 | Dial |
| 5 | 6 | Bracelet or strap |
Blocks 1 and 2: family and model
The letter L and the digit after it place the watch in a broad family, and the three digits that follow identify the model within it. Together they tell you the collection, the case size and the kind of movement. Some examples from the references we stock most:
| Reference begins | Watch |
|---|---|
| L3.781 | HydroConquest automatic, 41 mm |
| L3.790 | HydroConquest GMT |
| L3.810 | Spirit, 40 mm |
| L3.812 | Spirit Zulu Time, 42 mm |
| L3.802 | Spirit Zulu Time, 39 mm |
| L3.410 | Spirit, 37 mm |
Within a line, a change in these digits means a different size or movement. The 42 mm Spirit Zulu Time is L3.812 and the 39 mm is L3.802. If you are choosing between sizes, this is the block to read.
Block 3: the case material
A single digit gives the material of the case. Two are worth knowing by heart:
- 4: stainless steel
- 1: titanium, as in the titanium Spirit Zulu Time
Other digits mark gold, two-tone and coated cases. For those, read the Case material line of the specifications, which states the metal in words.
Block 4: the dial
The two digits of the fourth block identify the dial. Within a model, each color has its own code. In the 41 mm HydroConquest in steel, for example, L3.781.4.56 is the black dial and L3.781.4.96 the blue one.
Dial codes are not a universal color chart, so the same two digits can mean something else in another family. Use the photographs to confirm the color; use the code to make sure two listings are the same watch.
Block 5: bracelet or strap
The last digit tells you what the watch is worn on. In the sports lines:
- 6: a steel bracelet
- 9: a rubber strap
- 2: a leather strap
So L3.781.4.56.6 is the black HydroConquest on a bracelet, and L3.781.4.56.9 is the same watch on rubber. L3.812.4.63.6 and L3.812.4.63.2 are the same Spirit Zulu Time on a bracelet and on leather.
This is the digit that most often explains a small difference in price between two otherwise identical listings.
Three references, read in full
L3.781.4.56.6 HydroConquest automatic 41 mm (L3.781), steel case (4), black dial (56), steel bracelet (6).
L3.781.4.76.9 The same HydroConquest in steel with a different dial (76), on a rubber strap (9). We have 4 in stock.
L3.802.4.63.6 Spirit Zulu Time 39 mm (L3.802), steel case (4), dial 63, steel bracelet (6).
With or without the dots
Longines writes its references with dots, and you will also see them without: L37814566 is the same as L3.781.4.56.6. Both forms work in the search box on our site.
Reference number or serial number?
- The reference identifies the model, and is printed on the warranty card and the hang tag.
- The serial number identifies one watch and is engraved on the case back.
Longines keeps unusually complete records of its production. For an older watch, the brand can issue an Extract from the Archives based on the serial number, confirming when the watch was made and where it was first sent. It is one of the pleasures of buying a vintage Longines.
Using the reference when you buy
- Blocks 1 and 2: confirm the model and, above all, the size.
- Block 3: steel is 4.
- Block 5: bracelet, rubber or leather.
- Compare like with like. Match the whole number when you compare prices.
The movement also matters with Longines, because the brand sells quartz and automatic versions of similar-looking watches. The Movement line in the specifications states which one a watch has. Our guide to automatic and quartz watches explains the difference.
For help choosing a line, see our Longines buying guide, or browse the HydroConquest, Spirit, Master Collection and Conquest watches we have in stock.
Frequently asked questions
What does the 4 mean in a Longines reference?
In the third block, 4 means a stainless steel case. L3.781.4.56.6 is a steel HydroConquest.
What does the last digit of a Longines reference mean?
It describes the bracelet or strap. In the sports lines, 6 is a steel bracelet, 9 is a rubber strap and 2 is a leather strap.
Is L37814566 the same as L3.781.4.56.6?
Yes. The dots only separate the blocks; the watch is the same.
How do I tell the size from a Longines reference?
The first two blocks identify the model, and the size is part of the model. The 42 mm Spirit Zulu Time is L3.812, for example, and the 39 mm is L3.802.
Where is the serial number on a Longines?
It is engraved on the case back. Longines can use it to issue an Extract from the Archives for older watches.
Is Watchflix NYC an official Longines retailer?
No. We are an independent retailer and are not affiliated with Longines. Every watch is checked by our specialist before it ships.
