For most of us, a calculator might have been superseded by Excel or an app on a phone, yet there remains a die-hard contingent with a passion for the push-button marvels. So the shocking discovery of an apparently rogue HP-12C has sent tremors through the calculator aficionado world.

The HP-12C [PDF] is a remarkably long-lived financial calculator from Hewlett-Packard (HP). It first appeared in 1981 and has continued in production ever since, with just the odd tweak here and there to its hardware. //

A sibling, the HP-12C Platinum, was introduced in 2003, which added to the functionality but retained the gloriously late '70s / early '80s aesthetic of the range. According to The Museum of HP Calculators, "While similar in appearance and features it appears to be a complete reimplementation by an OEM (Kinpo) based on scans of HP manuals provided by the museum." //

"Testing our rogue HP-12c, it returned a result of 331,666.9849, from a true result of 331,667.00669… giving it an accuracy [defined here as the negative logarithm to base 10 of the absolute error] of 7.2, somewhere between the HP-70 of 1974 (1.2!) and the HP-22 of 1975 (9), but far off the 10.6 achieved by the regular HP-12c and 12.2 of the HP-12c Precision." //

Not knowing about the issue at the time, Murray posted his findings on forums dedicated to the calculators – the joy of the World Wide Web is that there is a forum for everything – and after some initial skepticism, members soon weighed in with suggestions. Was this a counterfeit? It didn't look like it. Maybe the firmware was rewritten as a cost-saving exercise? Perhaps...

Some speculated that HP – or perhaps a licensee – was rather hoping that by loading up the channel with versions featuring the original firmware the problem would go away and remain unnoticed.

However, no company should reckon without the sleuthing efforts of Murray and his fellow enthusiasts when things don't seem to be... er.... adding up. ®