The Zodiac Aerospace GMT


Introduction

After the success of the Sea Wolf, Zodiac introduced the Aerospace GMT using essentially the same case, with a 24 hour bezel which could rotate in both directions.   The advertisement below shows the Aerospace GMT together with the Datographic Sea Wolf, and it is thought to have been introduced in about 1962.

Zodiac GMT

 

As the GMT had an extra 24 hour hand, the advertising theme for the GMT was "Twice as much time for your money".

ad gmt

The advertisement reads : 

ad gmt cont

The watch did not have a settable 24-hour hand, and the two hours hands were geared together.   The rotating bezel allowed setting of the GMT offset.

The Movement

In the early 1960's the Zodiac Sea Wolf acquired a date complication, and the Sea Wolf Datographic, model 722-916 was launched.   722 referred to the signed 17 jewel Zodiac calibre 70-72 automatic movement which was introduced in 1961.  The movement is hackset, and the calendar function is quickset (old style).

This very successful AS calibre, later with 21 jewels was produced under the Communautee Horlogere de Precision, and was also used by Doxa, Girard Perregaux, Favre-Leuba, and Eberhard & Cie. for their men's automatics during the 1960's.

The calibre 75 had a 24 hour function and was used in the GMT.  Some GMT models had a 24 hour movement marked 70-72.

Later GMT watches used the calibre 75B with a quickset date function, and the Calibre 76.

Cal 70 zodiac

First edition  752-925

The first model is shown below, and came with a polished plated bezel which rotated in both directions, and with a green triangle at 0/24.  The 24 hour hand was an arrow with lume in the arrow head, the hour and minute hands thin baton with lume tips, and the second hand was a thin pointer. 

 

chrome aerospace gmt

Later bezels were patinated.

725-925 zodiac

Both white and black dial versions were available.

forst gmt zodiac

The case back was engraved, ZODIAC,  WATER & SHOCK RESISTANT, AUTOMATIC - ANTIMAGNETIC - SWISS.   There was a scale logo opposite the ZODIAC logo, see below.

Later models were waterproof to 20 Atmospheres as was the Datographic Sea Wolf which used the same case. 

 

 aerospace case back 

Early models were fitted with Cal. 70-72 or Cal. 75 movements, a Cal. 70-72 is shown below. 

cal 70-72 GMT aerospace

The case is 35mm (excluding crown) 38mm (inclusive), a slim watch at only 11mm thick.  Snap down case back.  

A Cal. 75 movement is shown below.

cal 75 zodiac

An early model with a 2 tone bexel is shown in its original case and $110 price tag.  The second hand on this watch is thought to be a replacement.

Aerospace GMT

The watch from the side showing the crown and milled bezel.

gmt aerospace

 

Aeronaut 752-925

The same model number was used for the virtually identical Aeronaut, except that Aeronaut replaced Aerospace GMT on the dial.

The hands on both models are those used on the Aerospace Jet 758.  Zodiac launched a line of 24 hour watches in 1962 as the Zodiac Hermetic. Over the years, the named changed to the Aeronaut Jet and finally to the Aerospace Jet. 

Given the history of name changes for the Hermetic, it is probable that the Aeronaut name was superseded by the Aerospace GMT.     However, the Aeronaut used the Cal. 75 movement.

Zodiac Aeronaut 

The model number and case back were identical to the (later?) GMT.

aeronaut case back

This model also came in white and in black dials.

aeronaut in black 

The 1962 Zodiac Hermetic with the same hands as the Aerospace GMT, is shown below.  This has Cal. 721.  

This was Zodiac's only 24 hour watch, and the dial is deep black combined with red markers for the odd hours and Arabic numerals for the even hours.  This watch has a snap caseback which features the water-resistant system that was similar to the one found in the Sea-Wolf. This feature explains the name "Hermetic" as well as the fish engraved on the case back.  The fish is where the scales are engraved on the Aerospace case back.

hermetic about 1962

 

 

Second edition  752-925

Later, the dial changed to one with baton hands, with longer pencil lume inserts, a red 24 hour hand with a lume tip, and a rectangular lollipop second hand.   The case back with the scale logo continued.

The indexes remained narrow, but now had lume dots on the inside.  The indices at 6, 9 and 12 were fluted.

A crossover model is shown below with the new hands, but the old 24 hour hand.

crossover gmt

Image courtesy  :  Hobart Town Antiques

The patinated bezel model is above, and the polished bezel below.

second gmt

 

gmt zodiac

The original case back with the engraved scale logo continued, a model with an engraved case back is shown below.

scales case back gmt

The case back later changed to the 20 atmosphere diving version, with Aerospace beneath Zodiac.

 gmt v 2

20 atm case back

ZODIAC AEROSPACE, ZODIAC logo, "AUTOMATIC - SWISS" and  "20ATM - WATERPROOF"

This is the same as the Sea Wolf case back with Aerospace instead of Sea Wolf.

Black dial versions are more common.  Thin pointer second hands were used.

Kaplan gmt

Image  courtesy  : Kaplans Auctioneers

The Kaplans catalogue reads :

ZODIAC, Aerospace GMT, Ref no. 752-925, men´s wristwatch, 35 mm, steel, self winding, plastic crystal, date, 24-hour indicator, original bracelet, foldingclasp, Ref no. /9, approx 1965.

A two tone bezel model was also available.

752-925 zodiac

Third edition  752-925

Then the model changed to wider indices, and a sweep second hand with a rectangular lollipop.  Some models continued to use the scale engraved case back.

first edition zodiac gmt

gmt aerospace zodiac

10k solid gold bezel version.

gold cap GMT

 omega bigdubnick

Bakelite version 752-934 and -934B

Around 1968 the bakelite bezel was used on the 752-934 series.   The Cal 75 movement was used.   The wide indices continued.  Later the Cal 75B and Cal 76 movements were used and the case back was engraved 752-934B.  this was also referenced model number 1975W.

A model with a grey/black bezel and the original stretch band is shown below.

752 - 934 zodiac

 

934 case back

 

 

 

 

 

 

 

 

Images courtesy Watchuseek user : tomvox1

A variety of bezel combinations are shown below, all with a black dial.

gmt zodiac blue black

blue black gmt

 

  

 

 

 

 

 

grey gmt

red gmt

 

 

 

 

 

 

Perhaps the most coveted is the Pepsi dial.

pepsi gmt

Cal . 75B 

75b cal

 

The 752-934B model had wider flatter indices.

934B

Cal. 76

cal 76

934b case back 

Images courtesy Omega forum user :  jinson

 World Time version 752-934B

Then the 752-934B became a World Time model as shown on the right below.

Cal 75B continued to be used in the same case with Aerospace still engraved on the case back.     Below is a comparison between the -934 models, together with a contemporary Sea Wolf in the same case..

The World Time has a grey dial and 1 ring of cities on the bezel.

group shot

Image Omega Forum user : bigdubnick

Later models had 2 rings of cities on the bezel.

zodiac world time

 

world time

 

Recommendations

The grail

There are few Aerospace GMT models around and any of the models would be an asset to any collection.

The grail would be the 752-934 complete set, with 2 tone bakelite bezel.

752-934 complete set

Perhaps even a Pepsi dial !

pepsi aerospaceaerospace stuff

Images courtesy Uhrforum user : mgvogt


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