At that price it’s probably a Rockbass but the 5 knobs has me stumped. 
Probably best to go back to the shop to get some pics and then we should be able to help identify it.
If you get the serial number from the back of the headstock you can check the specification with Warwick online.
en/Warwick—Support–Serial-Number.html
That said, as @RuknRole said, a StingRay would be a great choice for some slap antics.
What @HowlinDawg said.
The last 2 digits of the serial number will tell you the year of manufacture.
The early Rock Bass models do not have the best reputation.
It also may be worth asking the store to check if there is any movement in the truss rod to allow adjustments. I’m seeing a lot of very nice early German Warwicks up for grabs that have reached their adjustment run out and still the sellers are asking high prices.
I have one in my eBay watch list that has had its neck repaired and has 2 visable screw heads in its fretboard!
I love my Warwicks but in all honesty if I was going to grab a $500-$600 bass it would have to be a Ray4. Great value for money, very playable and (if you wanted to ) easily upgraded
I can only add my own experience.
I have a Squier Vintage Modified Jazz bass, purchased used for just under $300. I put $150 into pickups, another $75 into custom wiring and an upgraded control plate with better pots and output jack, and another $130 for a good luthier to put it all together and set it up for me.
So for about $650usd, I have a jazz bass that plays like a dream. It is now waiting for me to improve my slap technique to really show off what it can do.
Bottom line, a Squier vintage modified or classic vibe is a great mod platform, if you want to go that route. Heck, they sound pretty great out of the box. One of those or a Sire Marcus Miller will get you to 90% of where you want to be. Probably 99% with a good setup.
There’s basses I could recommend, but what are your choices? One thing I’ve learned is cost and availability vary greatly across EU. Especially with Fenders
That being said, Squier Paranormal is a good Jazz platform.
This is the most valuable thing I have been given/shown/educated about on this forum. Sorry that it’s off topic.
I always knew this as a Python skit - never realized it was pre-python. And this is quite possibly the only thing I’ve seen Marty Feldman in other than Young Frankenstein… 
Same! Had no idea it predated it.
I’ve got a squier Affinity Jazz bass, it works great for slap.
Now that you mention maybe I was mixing things up and it was another model that had the 5 knobs, I was shown too many basses in too little time 
Something I mentioned in another thread. I have a MIM Fender Dimension with single MM pickup. They are not very popular but built very well and go for low used prices. $450 USD so maybe similar in Europe. I was going to sell mine but when I was playing around with slap I found it was doing better than my J’s so I ended up keeping it. Electronics are active if that’s your thing. I prefer passive but its earned its place in my arsenal, for now.
I’ve found this Fender jazz bass from a local second hand seller, he says it’s a MIM, not sure if this is the same bass that you mention as this one has two pickups; seems to be in perfect shape and sells it for 600 € = 690 $, would you say it’s a good option given he price? I really love the looks of this bass. I’ve found it new at Thomann at some 870 $ plus shipping.
MIM = Made In Mexico.
Player series are fine instruments.
If it’s in excellent to mint condition from a reputable shop and with a warranty then it’s probably about the right price.
If it’s a private sale (i.e. not from a music shop) then the price is a little high and you should be able to haggle them down.
Thanks so much for the tips, I’ll let you know the outcome of my search 
I’ve had two Player series Jazz and they’re fine instruments, though I preferred the maple fretboard over pau Ferro. That could just be personal preference.
You have to be careful comparing prices in Europe with those in North America. I have always found Europe to be noticeably more expensive than the US or even Canada for that matter. A good price in Europe may not be as great as the US. The $650 price tag is about $150 bucks off from brand new at Sweetwater.
Seeing your from the east (I use to live more central) I think that is a decent price especially if it is in very good condition. I have a couple of Player editions and they are well put together minus maybe the pickups (decent but nothing great). Their satin finish necks are very smooth to play on.
Unlike Wombat I prefer either rosewood or pau ferro. Pau ferro gets a bad wrap but I am not sure why. I avoided it for quite awhile but ended up getting up a P bass Sunburst with PF (for a veyr good price brand new) and thought it matched the body nicely cause of the lighter/dark streaks. I have a maple neck Fender and I’m trying to love it but keep going back to my rosewood J’s or Pau Ferro P. In the end, if the wood was good enough for Roger Sadowsky to use in his amazing creations then it couldn’t a subpar building material.
Agree with all of this. I also have a Player Jaguar, and I switched out the pickups and it’s top notch now. One of the nice thing about Fenders is it’s super easy to find upgrades for them that fit with no adjustments needed. Pickups are an easy change to make, though it sounds daunting.
My fretboard of choice is Ebony, which is what I have on my player Jaguar. My newest bass which arrived today is Jatoba, which at first blush is pretty nice. Need to play it some though. I do like Rosewood too, have that on my Surveyor 400.
Have you considered a used Modified Jaguar Special HB? Mine’s my workhorse and I do a lot of slap with it. Sometimes they’re hard to find, but there’s quite a few on Reverb right now. Won’t break the bank, either!
Best budget slapping bass has got to be the sterling Ray4. Mm pickup and jazz neck=fun
You can use any bass to slap, it’s not so much about the bass but the strings. Round wound sounds best slapping, flat wound will sound much duller.
Just a remark, I’m from Andalusia in Spain, so not from the east but from the European " far west " 
Thanks so much for all the insight!
Thanks for the tip! Had no idea about Reverb, will have a look.
You’ve mentioned a Modified Jaguar Special HB, from the search I’ve done I think it’s a Squier bass, is this right?
I’ve come across some very good reviews about Squier jazz basses, namely a Squier Vintage Modified Jazz Bass:
I’ve seen many Squier basses at a local store in Seville where I live, brand new at a very decent price tag I’d say :
Truth is I really love the looks of these “Marcus Miller-ish” basses, and if a Squier jazz bass is a good instrument I think I’ll seriously consider it.
Besides this, I’ve seen dozens of Marcus Miller basses at this same shop:
They look absolutely the same to me as a Fender jazz bass or a Squier and at reasonably good prices, are they any good?
Thanks again!