A Dutch IWC Automatic

Hello everyone,
Impulse purchase last month on the 'bay from a Dutch seller with bad pictures. This is my first IWC and, with the preponderance of redials with the brand, I'm not sure where to start my foray so I'd like to submit it here for vetting.

A few observations:
1. The dial shows its age, with light spotting that can be magnified in bad light. The font is crisp and looks ok from first glance, but since I'm inexperienced with IWC dials it doesn't tell much.
2. Caliber 8521 or 8531 fron the date placement, but I can't get the case open. Someone tried to force it open and left some bad marks on the caseback(shame) and I'm afraid to do the same. Any tips on opening this or should I take it to my watchmaker? This doesn't seem like a screwback.
3. Minute hand is ever so slightly bent. Hopefully a competent watchmaker will be able to fix it.
4. Caseback is engraved "HEYKOOP GOUDA HOLLAND". Almost sounds stereotyped. I presume this referts to the town and not the cheese?
5. Originally it was on a Fixoflex bracelet, but since it's a bit big I have it on a strap. Would the correct buckle be the rectangular one?(image attached)
6. Where could I find the reference for this case? I cant quite pin it down from the catalogs I have seen on the net.

I paid 480EUR for it. I think I did not overpay? Thankfully the seller accepts returns so I'd love to see your opinions on this one especially if there are any red flags. Thanks for your help and forgive my long winding account.

Additional photos: closeups magnifying the font and spotting under bad lighting
Also is the last photo a correct buckle for this?

Hello,

Congratulations on your 1st IWC, I personally really like these vintage IWC with Pellaton calibers👍

1- In my opinion, the dial is original. I have seen several of these and nothing rings an alarming bell to me. I'll let others confirm or deny me on this.
2- Usually, these IWCs have a snap caseback that clips onto the case. So it is opened using a watckmaker's knife. It should have a slight opening on the side to allow some room for the tool. If you aren't experienced with the procedure, I'll advise you to let your watchmaker do it.
5- From my experience, this buckle is seen on later models of IWCs but I can be wrong on that one. The topic of IWC buckle isn't well documented.
6- Generally the case reference is on the inside of the caseback. However, with those early pellaton references, it is not unusual to only have the serial number without any case reference.

Also, the crown seems to be a replacement (maybe during a service). It has a later version of the fish logo. Usually on the 8531 or 8521, the crown is either a blank one or has an earlier fish logo.

Looks good to me. Get it to a decent watchmaker for a service. And a decent price.

I love it and I think you got a helluva good deal at that price!

Thanks everyone!
I was worried something might be off but this ones a keeper now. I'll be taking it to my watchmaker and have him examine it(will post movement shots)

Looks perfectly legit to me.
Don't look for a reference number inside the caseback, since at that time IWC had only serial numbers of the movement and of the case, but (as opposed to Longines, for ex.) not the reference number.
Probably it's a 8531 from beginning 60's.
I own one very similar to yours and it's from 1963.
If you check the serial number at moeb.ch you have the year of production.