should i buy? PO 21533442101001

hi omega forum,
long time lurker - reading all sorts of info and looking at great watch pics.
opening my first thread so greetings to you all.

i've had my hesalite speedy for around 5 years now and have no complaints - well one i only get to wear it weekends as i'm a tradesmen and don't want to knock it around.
have thought a few times about a 2254 but never bitten the bullet - always fancied some kind of diver but i'm not keen on the seamasters skeleton hands.

i have seen a planet ocean (21533442101001 back dial, leather strap with clasp, silver 6,9 and 12, £6.3k on omega website) in a UK high street jewellers outlet. i thought a PO would be too big for my skinny wrist but it sits well and i like it.
the watch is sold as pre-owned, there's stickers on the back, its got a hang tag, pictogram card and master chronometer card. no box or warranty card.
the serial starts 84150XXX and they want 4k GBP. i haven't been able to date it. (baselworld 2015 for the cal 8900 is all i've found so far)

so my questions - do you guys reckon its a buy without the warranty card or box at that price? how long has this iteration of PO been around?
thanks in advance for your replies
regards

thank you
so it could be up to 8 years old.
and i have noticed i 've posted this in completely the wrong place. sorry mods

Once again highlighting the fact that the Planet Ocean hasn't been updated for 8 years.
Regardless of all the million and one iterations of it, the actual basic model is still the same 3rd gen.
I think the first one had about a 6 year shelf life before the 2nd gen, that only had 5 years. Nobody called it

I bought mine on November 2016 from an OB for $8500 AUD. The same watch is now listed on Omega's website for $11750 AUD. I just had it serviced after exactly 8 years on the wrist wearing it EVERY day which cost $1060 AUD for an official Omega service. So, this model is at least 8 years old.