Vintage Rolex Unusual Design

[sd17]

Hi,

I'm hoping someone can assist me. My sister in law was given a Rolex watch by her dad. The watch was given to him by someone years ago. It was always assumed that the watch is a fake as it is unusual. It is a quartz movement. And theres no crown on the winder. After purchasing my first rolex explorer 1 and becoming familiar with the watch I am leaning towards the watch being genuine as it is quite worn but still in very good condition. The look and feel of the face looks quality. The leather band is vintage and stitched and possible branding could have been worn out. I've searched everywhere and cannot find a watch that looks like this. Does this look familiar to anyone.