Silver Arrow dial/case mismatch?

Greetings. This Longines is advertised as a Silver Arrow, but the case is 18K and the back has no arrow engraving.
Also, the movement number indicates 1955, whereas I believe Silver Arrows were not made till 1956.
Any ideas on the authenticity of this piece? All pictures here:
https://watchesoflancashire.com/product/1955-longines-silver-arrow-18ct-rose-gold/



I've seen cases like the one above, but only with the dial below:
https://www.sellingantiques.co.uk/5...ose-gold-cal-23zsd-mens-vintage-watch-c1956/#