581-type case, the bottom cover.

581-type case, the bottom cover.

 

 

A581-type watch case is divided into two semi-steel and steel-based, there are several models, divided into pre-1960 years ago, less shell type and size of steel and semi-steel and 60 years after the reunification shape of the full / half steel. In the final phase of the "A581" model and full range of "581" was the cover model in case further adjustments have been unified with the back cover diameter 30MM (SS1 products and post the same) A581 case-back is not "A591" and peace Oriental Red bottom cover a total of 12 models. Early A581 case back with "Peace, The East is Red Model" as subsidence concave with six holes to open the cover, bottom cover are often coupled with the earlier group of small "steel" or "semi-steel" shell used in conjunction .

 

 

Since then, the words ""-shaped bottom edge. Another group of more the case back in 1963, printed factory serial numbers, it was pointed out that the chef had worked in the past was like a Swiss watch factory, like in the hope that each are marked with serial numbers on the watch, so a specially ordered from Switzerland Station ID code printer, but in the end because of its large manufacturing capacity, this machine can not bear this load, eventually abandoned, the last 63 years in addition to these products, no serial numbers stamped in the bottom of such forms and the back cover is also A581 series of rare species, but more should be relatively rare with the "trial" symbol and number engraved on the back cover of manual, name suggests with a "trial" word stamp trial was the product when the back cover A581, but with artificial 4-digit serial number engraved on the troops when a group specifically for the A581 with the bottom cover.