That 1981 Raleigh, if built from a frameset by a "pro" bike store, would almost certainly had a chainset with 42/53 rings, and a freewheel like 13/15/17/20/23/26, or 13/14/15/17/19/21. Half-step systems, like Sheldon says, were a 1950's and 60's thing. They may have been a product of underdeveloped rear derailleurs as well as fronts. Rear derailleurs have become steadily better at absorbing the slack chain created by a larger difference between chainrings. I'll cite the first Dura Ace group, which coupled a 130mm bolt pattern crankset with a minimum ring of 39t along with a rear derailleur which could absorb much more loose chain than a NR, Simplex Criterium, or similar.
David Feldman
<Classicrendezvous@bikelist.org> Sent: Tuesday, April 03, 2001 7:28 AM Subject: Re: [CR]The idle ramblings of a freewheeler.
> Steve Freides asked:
> > did racers half-step or only tourists?
>
> Yes, half step was pretty much the norm through the 1950s. The
> typical chainset would be 46-49 or 47-50. My '61 Paramount came with
> 49-52, unusually large for a half-step of the era.
>
> Early front derailers were so primitive that they wouldn't shift
> reliably on wider jumps.
>
> Sheldon "Loves Old Frames, But Not Old Derailers" Brown
> Newtonville, Massachusetts
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