Welcome to Bikeforums, [MENTION=431919]rosan[/MENTION]! And to this RIH thread.

What you've got there is a Cové-built RIH. It looks like the mixte version (unisex!) of the 'Speciaal'. The '55' tubing was Cové's hi-ten designation I think. I agree with [MENTION=429281]Auke[/MENTION]'s calculation of the build date: '81 or maybe a little later.

You'll need to turn the bike upside down to find the serial number. It will be on the bottom bracket shell IIRC.

Apart from the broken front fender it looks pretty much OK and original. Which is not so strange, as this is a good quality bike that will outlive you if you take care of it.

Clean, replace grease, cables and bar tape and you're good to go.