The Magnum Opus -- a great work -- lug design was first introduced to the press in 1950 as part of the "Latin Series". In 1951 the Mk II was introduced and remained a strong seller for the next 35 years. This lug pattern became the top-of-the-line model and established Hetchins as a "marque of distinction". The Mk III was introduced in 1987 with the change-over to Bob Jackson Cycles and is the current style.

Sixty-six Mk Is are believed to have been built.

It is likely that there was some short period of overlap between the Mk I and Mk II models, when Hetchin used up remaining stocks of Mk I castings although the Mk II had already been introduced.

Mk ii
Mk iii
Mk iii deluxe

Mk I


Above: 1950 Magnum Opus Mk I. Note the modest fork tang and down tube lug. Later Opuses were fancier.


Above left: 1950 MO Mk I top tube lug.
Above right: 1950 MO Mk I seat tube lug.



Above: the Mk II, with its longer tangs on the top tube, down tube, and fork crown, was notably more elegant than either the Mk I or the Magnum Bonum. The arrow shows the place where the stamped extension was brazed to the original casting. The seam was filed smooth to be invisible.


Above left: old style bb shell, to ca. 1965.
(but may appear later as well).
Above right: newer style
introduced ca. 1966.

The MO II is probably the most sought model by collectors, and is the one most cyclists associate with 'the Hetchins look.'

Click here for more on the Magnum Opus Ph II design.


The Mk II design had been based on cast lugs with added tangs; when castings became unavailable in the mid 1980s, Hetchins developed the Mk III series based on industry-standard long-point pressed-steel lug blanks. These blanks were modified by drilling, windowing, slashing, splitting, and adding tangs, thus continuing techniques used on earlier models (such as the Swallow and Keyhole designs from the 1960s & 70s).

The basic fleur-de-lis pattern was carried over from the Mk II. Compared to the Mk II, the Mk III lugs are simpler along the sides of the top and head tubes, but note the extra tang extending below the seat lug; also the tang behind the headset bearing is longer.

Right: Slashes in the head lugs, and split points underneath, are typical of the MO III.

Typical MO III
head tubes.

MO bottom brackets show many variations from 1987 to the present.

Mk III deluxe

The Mk III deluxe can be recognized by the extra cauliflowery lug points on the side of the down tube and on the head tube compared to Mk I, Mk II, and the standard Mk III. There is also a tang extending underneath the down tube (see right).

MO II seat lug.

MO III deluxe seat lug.

Mk III 953 stainless steel

Mk i
Mk ii
Mk iii

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