Eterna calibre: 520 movement review

Eterna calibre 520 was launched in the 1930’s Earliest reference I have seen: 1936. Base model was a sub seconds movement without shock protection. By 1941 They intruded the 520H that features shock protection, this variant was both used by the Axis and Allies during World War Two. The movement was also modified to feature a sweep second option knows as a calibre 520S. Later variants like the 520L and 520U are referring to upgrades in the shock protection designs. The movement was phased out around 1950. The movement itself tends always to have a high quality finish throughout. The movement layout is very similar to 1930’s Patek Philippe and IWC where the crown wheel and barrel are situated underneath their own separate bridges. 

520 basic non shock protection.
520H Shock protection
520L Shock protection
520U Shock protection 

520S Sweep seconds. 

Eterna calibre: 520

  • Made approximately: April 1935-1950
  • Made in Switzerland 
  • Power reserve 43h
  • 15-17 Jewels 
  • 18000 B/A
  • DM: 26.05mm
  • H: 4mm – 4.95mm (S)

Finishing tends to be of a high quality brush on the bridges with polished bellied edges and perlage on the base plate. The ratchet and crown wheel have a decent starburst finish. 

Surface finish on top side of the plate and bridges: 8 Points

Surface finish on screws: 10 Points

Surface finish on crown and ratchet wheel: 7 Points

Movement Jeweling: 6-7* points 

Movement design innovation (for ca 1935):  7 points

The Eterna base plate on the 520 is well decorated with perlage and some beveled edges. Winding/setting mechanism is well made. Note how the yoke lever has its own grove in the base plate to keep it seated. Gear train has a good finish. 

Base plate finish: 8 Points

Setting and winding mechanism: 7 Points

Gear-train finish: 8 Points

Movement durability: 7 Points

Bonus points for shock protection on later models: 3*

Calibre: 520

Excellent time keeping when in good condition

Accuracy: 9 points 

Power reserve of 43 hours is fair for 1935

Power reserve: 7 Points

Eterna calibre: 520 points summary: 

Surface finish on bridges and top side of base plate: 8

Surface finish top screws: 10

Surface finish on ratchet and ratchet wheel: 7

Movement Jeweling: 6-7

Movement innovative design for ca 1962: 7

Total possible bonus points: 3

Base plate finish: 8

Setting and winding mechanism: 7 

Gear-train finish: 8

Movement durability: 7

Accuracy: 9

Power reserve: 7

Grand total: 84-88*