A 1999 ABI Award Transtar weighs somewhere between 1250 and 1300kg loaded according to the adverts that I've just looked at Taffy.
There are a few things to consider when buying a used tourer.
Ascertain that the seller actually owns the caravan and is entitled to sell it to you. A CRiS hpi check will reveal the year of manufacture and the legal owner of the caravan
http://www.hpicheck.com/caravans.html.
Don't buy from any online auction website without seeing the caravan, digital pictures can and often do differ from the reality.
If you decide to buy ask for evidence of regular servicing. You wouldn't buy a used car for a couple of thousand pounds without knowing that the brakes work, caravans are equipped not only with brakes but also with 240v and 12v electrical circuits and LPG pipes and you need to ensure your and your loved ones safety.
Check the tyres and ask how old they are. Caravan tyre treads rarely wear out but the sidewalls of the tyres deteriorate and they need changing every five years regardless of tread wear. If the tyres are five years old or over factor in replacement tyres when agreeing on a price and don't forget the spare tyre.
Push the towing hitch right back, there should be resistance and it should slowly extend again. If this is not the case the brake overun mechanism and damper needs to be checked.
Ensure that the road lights including brake lights and indicators are functioning and while you are checking look for signs of water ingress in the light lenses.
Make sure that the awning rails are ok and not loose and that the lockers are ok and have the appropriate keys.
The next thing that we need to look at is the overall interior condition of the caravan The seller wants you to like the caravan and to feel cosy and at home in it but don't get carried away and omit to look carefully under seats, inside lockers, along the inside seams such as corners with the roof / floor/ walls. Look around the door and windows and gently lift the rubber surrounds for tell tale signs of black mould. Look behind the blinds and curtains for signs of damp, often black mould forms on the lining of curtains.
If there is a musty smell this is a sure sign of damp so be wary if the seller has the fire on and has sprayed air freshener when you take a look.
Look for bubbled interior wallboards or soft spots, these are also signs of damp which will render any used caravan worthless. If the floor is springy and creaky it will be a sign of delamination. This is fairly common and can be repaired, a competent diy-er could effect the repair or a mobile service engineer would probably do it. Factor delamination repairs into the agreed price if it needs to be done.
Check that the fridge, cooker, heater,water system including the pump and water heater are all working correctly.
Check the cassette toilet.
The overall condition of any used caravan is more important than it's age. An older well looked after caravan is always a better buy than a newer flashier model which hasn't been serviced or looked after.
Good Luck