Calibre 1520 and Calibre 1530

[Marrk]

I believe it was Larry who recently posted a link to an article on James Bond's watches. In the article, there was a discussion of the two calibres that came in the ref. 5513 — the cal. 1520 and 1530. The author stated that these were remarkably reliable and accurate calibres, and that the difference between the two was that the 1520 was cheaper because it had fewer jewels.

Can anyone elaborate on this? How many jewels in each? If jewels are bearings, which bearings are not jeweled in the 1520? Do any TRF experts perceive that there is an appreciable difference in this case between more jewels and fewer jewels.

Thanks.