The 3000psi will most likely be aluminium, and therefore legaly has 10 years between tests here, so if sites accept the 10 year cycle is usable, if they stick to the marked 5 years then a site won't allow it to be used3000psi 48cu cylinder - test before 07/2015
Luxfer cylinder - test before 09/2019
All forum sales require cylinders to be in date
But value wise it's cheap enough new (about £30 to £40), is worth less second hand and not usually worth the price of a retest, will be pricey to post and can't be posted with all methods
This would be best bundled with one of the guns
The 4500psi would be fibre wrapped. These are approx £150 new, tend to go at around £80 second hand but vary on the remaining life
There should be two dates marked, a final date (15 years after manufacture) and the next test date (5 year cycle)
Double check if 2019 is the next test date or the final test date - the longer it has overall the more it's worth to someone
(Again it would cost to send and can only be sent by some methods, but is more worthwhile)