Rebalancing my RPN portfolio


Over the past year I've been rebalancing my RPN calculator collection (aka portfolio), by selling off duplications in my HP RPN collection, while seeking out rare non-HP RPN calculators. By my count, I've sold 6 HPs (2 Woodstocks and 4 Classics), whilst acquiring 5 non-HP RPN calcs, the latest being a Commodore 4921. At this time HP RPN calcs represent approximately 59% of the total collection, while non-HP RPN calcs represent 18%. The remaining 23% are non-RPN calcs, although some of them are non-collectible elcheapo 4 bangers. About 90% of them are in good working condition, while the remainder of are in various states of disrepair and are mostly retained for spare parts, although some are junk that I really should just give away or throw in the trash. I really don't see myself acquiring any more vintage HP calcs and unless HP comes out with something really exciting in a new model, I may have bought my last HP calc. I'm selling off a few more HP RPN calcs that are duplicates, while still seeking to fill a few holes in my non-HP collection (anyone have a Privileg PR 55 NC they want to sell?).



Not a Privileg but the Hiradástechnika TK-1023.

Unfortunately is it since 2:00 PM Eastern time on TAS :-(




I saw all your listings on TAS. I already own a complete Novus Scientist 4520 in excellent condition with a new battery, which is the same as the TK-1023, so I'm not interested. In fact, I own virtually all the Novus / National Semiconductor RPN models. I also already have an Omron 12SR which I bought from you, along with a Corvus 500 and a APF mark 55. Now, if you can find a good Privileg SR 54 NC or PR 55 NC, then you'll definitely get my attention. :)



Michael; I'm not bidding on it either, but Joerg's TK-1023 does have one unique feature i have never seen on any of that family before. There's a yellow racing stripe down the middle. That should have been done to all the 41s with the speeded-up clocks.


Haha, good point. Tomorrow I'm going to the hobby shop to get a bottle of Testors bright yellow paint so I can put a racing stripe on my Novus Scientist.

On an unrelated note, I read your writeup on the Commodore 4921 on your website, and I think your statement that it has 10 registers is incorrect. I downloaded the manual from Katie's website, and it supposedly has only 3 registers (0,1,2), which are all used when performing statistical operations (sum n, sum x, sum x^2). Anyway, I won't know for sure, and that could be weeks from now, since it's comming from the UK.



mine stores and recalls numbers in 0 through 9.


Weird. I wonder if it's an undocumented feature. We are talking about the SR4921 RPN, correct? Do you have the manual? If so, look at page 24. Anyway, when I get mine, we'll find out for sure.


yep. 4921. & serial no. 15350. made in Hong Kong.
Mine may have a bug. It does have a red dot on the on switch.
i may be stretching things there.


Red dot or yellow stripe - triples the value of a calculator!



My Commodore SR4921 RPN arrived today and I observed that it indeed can store and recall numbers in registers 0 though 9, and in fact can also perform memory arithmetic such as M+ and Mx. But, wait, it is all an illusion, since in fact there are only 3 real independent storage memories and the values in memories 0 through 2 are replicated in the other phantom registers. Registers 0,4,8 are the same storage location, 1,3,5,7,9 are the same and 2,6 are the same. Store a number or perform storage arithemetic on any one of them, and the result will be replicated in the others. Use the statistical functions, and values will be stored in all of them, not just the first three. So basically, the other number keys have been mapped to the same memory locations, instead of giving an error indication as would be the case with most other caculators when attempting such an illegal operation.


well i'll be dipped in're right.
that was sloppy, or trusting, of me. any other calcs do this sort of trick? - other than the 41's sto a = sto 01, sto b = sto 02 etc.


any other calcs do this sort of trick?

The address code for TI-59/PC-100 printer characters did the same sort of thing. In that case it was the eights digit which was being ignored , not the fours digit as with your units.

That brings back some memories - one of those was my first calculator, beleive it did only have 3 registers and I remember that the trig functions were sometimes only a little better than using 4 digit trig tables, but it was easier to use!

It is amazing to think that it is now a sought after machine...

Mike T/


I think it's only sought after by RPN junkies like myself, but in time as we die off it's value will wane, and it will just become another ubiquitous antique calculator.



Well done!!! And it is NOT just a National Semi clone ;-))



Joerg; Very true. As you probably already know; the only 4 calculators listed in Meke Sebastian's Calculator Forensics website as having the same trig results are all Commodores.

Not that there's anything wrong with a Nat Semi clone.....


Speaking of clones, the Brazilian Dismac HF-90 is an OEM clone of the Commodore SR 4921 RPN, that uses the same Mostek MPS7561 chipset. It also has the same calculator forensic number, which is different from any of the NS / Novus models.

Possibly Related Threads...
Thread Author Replies Views Last Post
  [PRIME] RPN: another attempt at returning more than one value to the RPN stack Marcus von Cube, Germany 5 1,650 11-05-2013, 02:44 AM
Last Post: Marcus von Cube, Germany
  New Iphone & Itouch calculator - Access RPN and Active RPN Nigel Bamber 1 802 06-10-2009, 04:13 PM
Last Post: Jean-Michel
  Another calculator with RPN (Corvus 500 RPN) Saile (Brazil) 7 1,503 03-31-2009, 12:14 AM
Last Post: Michael de Estrada

Forum Jump: