The Zenith Chronomaster El Primero Full Open 38 mm reference 03.2153.400/78.C813 pairs an openworked dial with the automatic El Primero 400, a 5 Hz column-wheel chronograph movement. Zenith’s published specifications give it a 38 mm steel case, 12.75 mm thickness, date at about 4:30, and a minimum 50-hour power reserve. Those figures identify the watch; they do not establish how it wears, reads, or performs in use.
Which 38 mm Full Open is this?
This review focuses on Zenith reference 03.2153.400/78.C813: the 38 mm stainless-steel Full Open on a leather strap. Zenith’s August 2017 technical announcement lists it separately from two other 38 mm configurations. Zenith’s launch announcement is the primary source for the reference distinctions and specifications.
| Reference | Configuration listed by Zenith |
|---|---|
| 03.2153.400/78.C813 | 38 mm steel case, leather strap |
| 51.2151.400/78.C810 | 38 mm steel case with 18K pink-gold bezel |
| 03.2153.400/78.M2150 | 38 mm steel case with bracelet |
| 42 mm variants | Also listed in the 2017 announcement; the 42 mm layout places the date at 6 |
Strap, bezel, and date-layout details should be checked against the full reference rather than assumed from the Full Open name alone. Zenith’s current Chronomaster Open collection page supplies family context, but it is not an inventory page and currently returns no product results. That does not establish whether this exact reference is discontinued or available through a retailer.
What the openworked dial shows
The dial exposes portions of the movement rather than covering them with a conventional solid face. Zenith’s launch material describes an “entirely open – and openworked – dial enabling full visual appreciation of its high frequency.” That is the manufacturer’s description, not an independent assessment of legibility or visual effect.
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Zenith lists the following indications for the 38 mm version:
- Central hours and minutes
- Small seconds at 9 o’clock
- Central chronograph seconds
- 30-minute chronograph counter at 3 o’clock
- 12-hour counter at 6 o’clock
- Date between 4 and 5 o’clock
The date position is a useful identifier: the 42 mm version listed in the same announcement places it at 6 instead. Because the openworked dial reveals the mechanism behind the indications, photographs and in-person viewing are especially useful for deciding whether the display suits your own preference; published specifications cannot settle readability for a particular wearer.
Movement and chronograph specifications
Zenith specifies the automatic El Primero 400, a column-wheel chronograph calibre with date. The 2017 announcement lists a 30 mm movement diameter, 6.6 mm movement thickness, 326 components and 31 jewels. It runs at 36,000 vibrations per hour (5 Hz) and has a stated minimum power reserve of 50 hours. These are manufacturer specifications, not measurements from an independent timing or reserve test.
The 5 Hz rate is central to the Full Open’s presentation: the openworked dial makes the high-frequency movement part of what the wearer sees. Zenith’s current family page also discusses silicon escape-wheel and pallet-lever components in the broader Chronomaster Open description, but those details should not be attributed to this specific 2017 El Primero 400 reference without model-specific confirmation.
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Case, crystal, and water-resistance figures
For the steel 38 mm reference, Zenith gives a case diameter of 38 mm and thickness of 12.75 mm. The front crystal is domed sapphire with anti-reflective treatment on both sides; the caseback is transparent sapphire. The stated water resistance is 10 ATM, equivalent to 100 metres. That rating is a specification, not a blanket recommendation for any particular water activity.
Zenith’s 2017 launch announcement is the basis for these dimensions and construction details. A separate review search result gives a different thickness, but does not establish a directly comparable measurement method; the manufacturer’s stated 12.75 mm figure is therefore the clearest published specification to use.
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- Lug size: 22mm
- Buckle size: 18mm
Strap and clasp
The 2017 announcement lists black or brown alligator leather straps with a rubber inner lining and a steel triple-folding clasp among the family specifications. It does not establish which strap is fitted to every individual listing, so confirm the actual strap and clasp configuration against the reference and seller’s description. The steel-bracelet version is a distinct listed reference, 03.2153.400/78.M2150.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What this review can—and cannot—tell you
The published material supports a reference-specific account of the watch’s layout, movement, and manufacturer specifications. It does not support first-hand claims about wrist comfort, visual legibility, winding feel, timekeeping accuracy, finishing in hand, or measured power reserve. The cited 2019 video review is available as search-result metadata, not as a basis here for independent test findings.
Best Value
- Lug size: 21mm
- Buckle size: 18mm
Likewise, a current price, live stock, and production status for 03.2153.400/78.C813 are not established by the available sources. Zenith’s current collection page is not a stock listing, and the WatchCharts Canada page could not be opened to verify a valuation. Treat any seller offer as a separate, dated listing and check whether it is new or pre-owned, the exact reference, condition, included accessories, and market currency before comparing prices.
Verdict
The 38 mm steel Full Open is the El Primero 400 in a deliberately transparent format: a compact case by the model’s listed dimensions, a high-frequency automatic column-wheel chronograph, and a dial that puts movement architecture in view. Reference 03.2153.400/78.C813 is the precise 38 mm steel leather-strap model covered here. Its appeal depends in part on whether you want the mechanism to be a prominent part of the display; published specifications alone cannot answer the practical questions of fit, readability, or current value.
Quick Recap
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