International Workshop AC
João's second mystery slide rule
Brzail made circular slide rule
Click images for magnification
Data:
- Circular slide rule with two overlapping discs
- Scales K, A // C // D, L
- The upper disc is transparent and has a hairline and also a D scale.
- It was made to be distributed as a company gift.
- Made in Brazil.
Questions:
- Why was this construction chosen?
I have found a similar specimen in: www.duzzivintage.com.br/peca.asp?ID=8574014
“Lupa” (a female wolf like the statue symbol of the city of Rome) seems to be the brand.
There may be a register of patent (or the like) with number 73134/5 but only as paper copy (as “perplexity.ai” says) due to being earlier than 1975.
The back is for propaganda (with four rubber stoppers), both from Sâo Paulo (maybe the city of the manufacturer as well)
It has a structure like Fearns devices.
It seems the hairline is fixed at “1” in C scale covering only the three central scales (only pointing to first and fifth ones)
Jose Fernández
Some Fearns disks use a bolt as a pivot, as this disk, but others use a rivet, see ISRM. Are there any Fearns with rubber stoppers at the back? Andries de Man