The HP-15C is the Voyager most people want, and there are three of them. HP made the original from July 1982 to early 1989. Owners kept asking for it back, and HP obliged twice: with the Limited Edition in 2011 and, through its licensees, the Collector's Edition in 2023. They look nearly the same in photos, they run nearly the same software, and sellers mix them up. This guide covers what each one is and the checks that tell them apart.
The original HP-15C (1982 to 1989)
The original 15C arrived on July 1, 1982 with the 16C. It packed the most math HP ever put in a Voyager: matrices up to 8 by 8, complex numbers on a second stack, SOLVE for finding roots and a numerical integrator, carried over from the HP-34C it replaced. HP hired William Kahan to design the numerical methods. It has 67 registers, three of them always data and 64 that can become program memory, for up to 448 program lines.
It runs on three button cells, alkaline LR44 or silver-oxide 357. HP rated them at 6 to 12 months of normal use, with memory lasting at least a year and a half on alkalines if the calculator stays off. A flashing asterisk in the lower left of the display is its low-battery warning. HP stopped making it in early 1989, and as the Collector's Edition handbook puts it, prices for used ones rose steadily and former users pressed HP to bring it back.
The Limited Edition (2011)
HP announced the 15C Limited Edition on September 1, 2011, after showing a prototype marked 15c+ at a collectors' conference the year before. It looks like the original and runs the original firmware, but an ARM processor emulates the old chip at least 150 times faster, according to HP. User memory is unchanged. It runs on two CR2032 coin cells, which HP estimated last about a year, and you swap them one at a time to keep the memory.
The LE has two documented bugs, listed by the Museum of HP Calculators and cited by Wikipedia:
- PSE: in the release firmware, which the self-test dates 2011-04-15, the pause command works once in a program and then blanks the display until the program stops.
- Self-test: the original 15C's self-test keystrokes don't work on the LE and can corrupt memory. HP added an errata sheet and a new test menu, reached by holding g and ENTER while pressing ON.
Neither bug stops it being a fine daily 15C. If your programs use PSE, though, know it before you buy.
The Collector's Edition (2023)
The Collector's Edition was announced in May 2023 and shipped that July. It was made by HP's licensees, Moravia Consulting and Royal Consumer Information Products, and built in the Philippines. It wasn't made by SwissMicros, whatever some listings say. It has more memory than either earlier model, 672 bytes of program memory and up to 99 registers, and its handbook says typical operations run 10 to 20 times faster than the original. The contrast is adjustable, the LE's bugs are fixed, and a hidden menu even holds a mode that emulates the HP-16C. It's still sold new.
How to tell them apart
You don't need a serial number decoder for this. Four checks, all from the handbooks and Wikipedia, settle it.
- The batteries. Open the battery door. Three button cells mean an original. Two CR2032 coin cells mean a Limited Edition or a Collector's Edition.
- The low-battery warning. The original shows a flashing asterisk; the LE shows a battery symbol.
- The labels. The LE has Limited Edition printed below the HP logo and a back label in black text on brushed metal. The original's back label is white text on black. The Collector's Edition has Collector's Edition on the front, no Hewlett-Packard text along the bottom left, and a slightly darker brown case.
- The MEM test. Press g then MEM on a calculator with default memory. An original or an LE shows 19 46 0-0. A Collector's Edition shows 19 78 00-0, because it has more registers.
Speed is another clue. A long program or a matrix inversion that crawls on an original finishes almost at once on the LE. Ask the seller for a short video if the listing is vague.
Serial numbers
Original 15C serials are four digits, a letter and five more digits. Collector Tony Thimet reads examples like 2441A94505 as 1984, week 41, made in America: the first two digits plus 1960 give the year. The LE uses a different format; the one sourced example starts CNA, for China. You'll see claims online about special LE or CE serial prefixes. We couldn't confirm any of them, so use the batteries, labels and MEM test instead.
Clones
SwissMicros makes the DM15 family, from a credit-card size to a full-size model with a dot-matrix display. They're well made and run 15C software, but they aren't HPs, and the display gives them away in photos. There are also software 15Cs, including HP's own app. A listing that calls a DM15 a 15C is easy to spot if you look at the display and the branding.
Which one to buy
Buy the original if you want the 1982 calculator itself, its feel and its slow, deliberate chip, and you're happy to check a forty-year-old battery compartment. Buy the Limited Edition if you want a fast 15C and can live with the PSE bug. Buy the Collector's Edition used only if it costs less than a new one, since it's still on sale and it's the most capable of the three. If you don't need matrices or complex numbers, the HP-11C is the simpler Voyager scientific.
Checks for any 15C
- Battery compartment: clean contacts, no crust, and the right cells for the model in the title.
- Display: every digit complete with the calculator on.
- Keys: every key registers once per press, including the gold f and blue g shifts.
- Self-test: on an LE or CE, hold g and ENTER while pressing ON. A menu reading 1.L 2.C 3.H is what you want. Don't run the original's self-test on an LE.
Our condition checklist covers checking any older HP in more depth, and the Voyager page lists every model in the line.
