Believe that you may well be correct about the method of decoration, which does look as tho it may well be 'machine etching' (the bowl is covered in a resist - the pattern is then outlined on the resist by a machine, so when dipped the acid cuts only where the pattern has been drawn) - someting that was quite common in the earlier part of the C20, although more often seen as spiral patterns and greek key designs. These fine lines are quite typical of this method. Unfortunately, you don't say what the underside of the foot is like - which will give a better clue perhaps to age/quality etc. i.e. pontil marks etc. (or not).