There’s a mystery on the walls of almost every Toronto subway station. It’s in the leg of the letter R, the tail of the Q and the angle of the S.

The station name, etched in big, round characters along the length of the platform, is written in a distinctive Art Moderne lettering unique to the Toronto Transit Commission.

Despite its prominence and importance to the TTC brand, though, the identity of its creator has remained an enigma for more than half a century – as has the name of the person who created the TTC's famous logo, with its layered jumble of letters, around the same time.

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Open this photo in gallery TTC logo. Mark Blinch/The Globe and Mail

We do know that both were created in-house as part of a major rebranding of the TTC to coincide with the opening of the subway – Canada's first – in 1954, but precious little else.

How strange that two symbols of Toronto would go unclaimed, especially when there is such interest in the graphic design of the TTC, as evidenced by the popularity of its merchandise. The person who created the city’s most distinctive lettering deserves credit, if he or she can be identified.

There is a vast amount of material related to the construction of the Yonge subway line at the City of Toronto Archives – countless boxes of blueprints, minutes, reports and memos. Among these papers is an unpublished book manuscript written in the early 1990s by Walter Paterson, the chief engineer of the Yonge line. Some of it is printed on loose sheets of paper, some is on hand-labelled floppy disks.

According to Mr. Paterson, the first discussions about which type to use on the subway were initiated in the late 1940s by well-known graphic designer Clair Stewart, the art director of the firm Rolph-Clark-Stone.

Over lunch, Mr. Stewart “would emphasize again and again the need for simplicity in our designs,” Mr. Paterson wrote. “Clair told me that the London Underground had designed an alphabet that was outstanding for its clarity” and recommended the TTC study it.

That alphabet, called Johnston, was commissioned in 1913 and designed by graphic artist Edward Johnston. It remains widely used across the London Underground transit system.

“The printers told us it would cost a fortune to have special type cast for our job. We then found that ’21st Century Type’ was almost identical, and used it,” Mr. Paterson wrote.

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Open this photo in gallery The TTC Museum subway stop sign. Ryan Carter

The type he remembered was probably 20th Century, a close copy of the popular Futura font. Either 20th Century or Futura (it’s very hard to tell them apart) appears on TTC maps, pamphlets and notices to this day but, crucially, it is not the mystery type used in the stations.

Graphic designer David Vereschagin knows the distinctive platform lettering better than most. In the early 1990s, realizing it was under threat by unsympathetic station renovations, he began recreating the type from scratch from rubbings and photographs.

“I tried to figure it out,” he said. “Is it Futura? No, it’s not. It kind of looks like Futura, but no, it’s not. Is it Kabel? No, it’s not Kabel. So just what is it?”

He believes the type was most likely created by someone inexperienced, possibly a draughtsman with just a compass and set square.

“I wasn’t seeing any refinements that would normally be added to a typeface,” he said. “Somebody just took a compass, drew two circles, and that was their O.”

In a set of March, 1954, drawings in the TTC’s archival collection, the compass points are still clearly visible, and, on closer inspection, the lettering does appear remarkably simple.

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The legs of the R and K end at 45-degree angles, while the X and Y do not. The P and R are almost identical. Using a geometry set, it’s possible to almost perfectly recreate some of the letters in minutes.

Part of its allure is that we don’t know who did it. — Graphic designer David Vereschagin

The 1954 drawings are signed by Philip Butt, a draughtsman in the TTC’s architectural department during the construction of the subway.

If Mr. Butt did create the TTC typeface, this probably wasn’t the first time he had drawn it: Very similar lettering appears in a picture of a construction sign from 1949.

His signature also appears on a detailed drawing of the current TTC logo dated January, 1954, just months after it was hastily created following the sudden and last-minute rejection of another popular and widespread logo.

Around 1946, prominent mid-century architect John Parkin, who was acting as an adviser to the TTC, and chief architect Arthur Keith began working on an insignia that could be used at subway entrances and as a general TTC logo.

“Eventually, they came up with a proposal that [the Rapid Transit department] thought was pretty good,” Mr. Paterson recalled in his memoirs.

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It consisted of a horizontal bar containing the words “Rapid Transit” over a circle filled by the TTC initials.

The Parkin-Keith logo was used for almost eight years by the Rapid Transit department during the construction of the subway, appearing on hoarding, notices and internal documents. It was even recreated in the shape of the door handles at main entrances to the subway.

The TTC seemed set to adopt it as its official logo. But at the internal unveiling ceremony, TTC chairman William McBrien and general manager H.C. Patten flatly rejected it.

“So the insignia that I thought was a very good design, that carried a clear message, was abandoned,” Mr. Paterson wrote.

In its place, the TTC adopted its current logo, which was quickly designed by the winner of an internal competition among the architects. Sadly, Mr. Paterson doesn’t credit the designer in his memoir, and neither did TTC internal magazine The Coupler when the design was unveiled in August, 1953.

We can’t know for sure if it or the typeface were created by Mr. Butt, not unless more evidence comes to light. Mr. Butt died in the 1960s, a few years after leaving the TTC at the age of 70.

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Ian Dickson, the TTC’s current manager of design, doesn’t agree the subway typeface was the work of a draughtsman, however.

“I sense probably a professional typographer did it because, even today, to match the letter kerning [the space between the letters], especially, on the Bloor line, it’s challenging to make it any better than it is.”

For Mr. Vereschagin, the joy of the lettering is its inscrutability.

“There is a certain satisfaction in it still being a mystery,” he said. “Part of its allure is that we don’t know who did it.”