Never saw that fork crown in many years of monitoring Olmos on eBay, nor saw it when I’ve searched the web to find Olmos with serial numbers. I’m impressed that you recognized it as being the Olmo star head tube decal with the word Olmo. As you say it was probably immediately before they changed the fork crown to the pointed star with Olmo lettered underneath, (and definitely before the rounded star head tube decal). Probably a 1976 bike (?)