The Stronglight 49D first made its appearance around 1936 or so. Front deraillieurs were rare (but not unheard of) so a single ring was most common.
Around 1949 Stronglight often packaged their crank with a single road ring in a nice blue box with a remover included. So rather than odd, this was in fact a very common version. In the UK market it was probably very common too as single chainring bikes with deraillieur gears were commonplace.
Mike Kone in Boulder CO
> Thomas Adams wrote:
\r?\n>
\r?\n> What's odd to me is the single TA style road width (3/32) chainring, with no
\r?\n> provision for attaching inner rings. I thought the model 49 was a two ring crank
\r?\n> from the start.
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\r?\n> ----
\r?\n>
\r?\n> One sees these all the time on bikes in the V-CC News & Views, for it
\r?\n> was a common way to set up a bike in the 1950s, when British riders often (but
\r?\n> by no means always) used only one chainring. The number of rings to use on a 49D
\r?\n> was up to the individual, and TA even offered a four ring combination. Remember
\r?\n> that TA made rings for the 49D and cranks of the same pattern from Williams,
\r?\n> BSA, etc. for some years before they made their own cranks. Chain rings not
\r?\n> drilled for mounting an inner ring have been available from TA probably for
\r?\n> decades. I have one on my bike.
\r?\n>
\r?\n> Christopher Barbour
\r?\n> Boston, Mass.