Vintage 1988 HP 28S Advanced Scientific Calculator RPN Programmable Made in USA!

SG Retro Tech
(53)
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US $94.95
ApproximatelyRM 401.00
or Best Offer
Condition:
Used
“Tested and fully functional. Display is clear and responsive. Keys show light cosmetic wear ”... Read moreabout condition
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Located in: Gardner, Kansas, United States
Delivery:
Estimated between Fri, 31 Oct and Thu, 6 Nov to 94104
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30 days return. Buyer pays for return shipping. If you use an eBay shipping label, it will be deducted from your refund amount.
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eBay item number:167861441232
Last updated on Oct 25, 2025 12:26:46 MYTView all revisionsView all revisions

Item specifics

Condition
Used
An item that has been used previously. The item may have some signs of cosmetic wear, but is fully operational and functions as intended. This item may be a floor model or store return that has been used. See the seller’s listing for full details and description of any imperfections. See all condition definitionsopens in a new window or tab
Seller Notes
“Tested and fully functional. Display is clear and responsive. Keys show light cosmetic wear ...
Model year
1988
RPN Logic
Yes
Power Source
Battery (3 × N-cell)
Color
Dark Gray / Silver
MPN
HP-28S
Vintage
Yes
Programmable
Yes
RPN Capable
Yes
Form Factor
Clamshell design
Made in USA
Yes
Display Type
LCD (Multi-line)
Algebraic Entry
Supported
Graphing Capable
Yes
Data Communication
Infrared (IR port)
Country of Origin
United States
UPC
0088698000106
Category

About this product

Product Information

The HP-28 is a series of scientific calculators introduced by Hewlett-Packard in the late 1980s. The first model was the HP-28C. It was released in 1987 and had only two kilobytes of RAM or random access memory. A year later, HP released the HP-28S model, the second and last in this particular line. This was a more advanced scientific calculator and had a capacity of 32 kilobytes of RAM. These were among the first scientific graphing calculators, which means that they had the capacity to solve calculations graphically. The HP-28S became the more common and popular calculator of the two. It is a lightweight handheld scientific and graphing calculator that weighs in at a mere 7.2 oz. It is pocket sized and offers just the right balance between power and ease of use. It has a simpler menu structure yet still provides multiple programming options. The display is 137 x 32 pixels with a dot matrix, monochrome LCD. This allows for four lines of data to be displayed on the screen. The calculator provides direct entry for algebraic formulas and an RPN input logic for interactive calculations. The information is displayed in a dynamic way with infinite stack viewing. This calculator performs a number of specific functions. You can perform algebraic manipulation, which means symbolically solving equations for any variable. You can do calculus, calculating derivatives, and definite and indefinite integrals. You can also solve math linear equations and perform binary bit manipulations. Users can calculate single and paired-sample statistics and probabilities and plot them on a graph. Finally, you can make unit conversions using any of the 120 built-in unit combinations.The 28S uses a regular battery, so you don't have to invest in special batteries. It has a protective clamshell case that flips open and comes in a variety of colors. The left side of the cover features a QWERTY alphabetic keyboard, while the right side features a regular scientific calculator keyboard. The unit has a regular key size. The power comes from a custom chip containing an improved Saturn processor core that runs at 1MHz. This new mini processor was so special that it was given a codename of Lewis. Each style of processor had a particular name taken from the Lewis and Clark expedition. Each provided something innovative, and this one provides the user with a file directory system. This is used for filing variables and storing functions and programs to use later. The HP-28S calculator offered a series of firsts. It was the first to offer RPL, or Reverse Polish LISP, as its programming language and was the first scientific calculator capable of symbolic computation. Even with all the capability, the 28S is simple to operate. There are four editions of manuals that you can use as guides. With these innovations, the HP-28S is a reliable device for solving advanced equations.

Product Identifiers

Brand
HP
UPC
0088698000106
Model
28S
eBay Product ID (ePID)
166527924

Additional Product Features

Power Source
Battery
Size
Pocket
Key Size
Regular
Type
Scientific

Item description from the seller

About this seller

SG Retro Tech

100% positive feedback•57 items sold

Joined Jul 2025
Usually responds within 24 hours
SG Retro Tech — Rescuing the Past, One Discovery at a TimeSG Retro Tech rescues vintage electronics, gaming gear, and classic media from the scrap heap — restored, tested, and ready for a second life. ...
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  • a***m (78)- Feedback left by buyer.
    Past month
    Verified purchase
    Literally the best purchase experience ever! Arrived early, extremely well packaged and better than I imagined. The condition of the box and tapes is practically brand new, and the sound is perfect, just as I remember it. Better than described! Seller had amazing communication all the way through, and the value is amazing. Very happy, I completely recommend this seller A+++++ Thank you!!
    Reply from: sgrt-mg- Feedback replied by seller sgrt-mg.- Feedback replied by seller sgrt-mg.
    I’m so glad this set brought back great memories for you! It makes me really happy to have played a part in helping you reconnect with something from your childhood. Thanks again for the kind words and for letting me be part of that experience.
    The Hobbit – Mind’s Eye Radio Drama 6 Cassette Wooden Box Set COMPLETE Parts 1–6 (#167746299868)
  • 3***3 (155)- Feedback left by buyer.
    Past 6 months
    Verified purchase
    Excellent seller. Answered questions immediately, maintained great communication. Item exactly as described. Great price. Very fast shipping. Would definitely shop with them again.
    Reply from: sgrt-mg- Feedback replied by seller sgrt-mg.- Feedback replied by seller sgrt-mg.
    Hello helder33, Thank you so much for your feedback! I truly appreciate you taking the time to share it. I’m glad to know you’re happy with your purchase, and it was a pleasure doing business with you. Best regards, Michael SG Retro Tech
    Seagate Portable 2TB External Hard Drive HDD USB 3.0 – PC/Mac/PS/Xbox NIB Sealed (#167733715615)
  • c***i (162)- Feedback left by buyer.
    Past month
    Verified purchase
    Exactly as described. Excellent communication and packaging.
    Reply from: sgrt-mg- Feedback replied by seller sgrt-mg.- Feedback replied by seller sgrt-mg.
    We really appreciate your kind words and feedback! We're glad the calculator arrived just as expected and that you were happy with the communication and packaging. Michael / SG Retro Tech
    Texas Instruments TI-30X IIS Scientific Calculator Pink New Sealed SAT ACT AP (#167782569706)
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