Its easy to see if you look for the correct things, on an RVF400, if there are no small dragger pieces under the foot pegs, it coule be a sign of a drop, same goes for the lower fairing fixing points, there are small L shaped brackets that hang off the chassis and hold the fairings more securely, most RVF400's would be missing these. Other tell-tale signs of previous accident history are aftermarket bar ends, aftermarket brake/clutch levers, footpegs, and obviously the aftermarket fairings.

If anybody tells you that they changed the RVF panels to Tyga panels only because it looked better, and they dont have the original panels to proove this, its obvious they have had an accident. Dont forget, original RVF panels cost 4x the price of Tyga equivalents new. Finding second hand ones, well good luck with that... I had to import RHS panels last year for my one which set me back around $500 just for the RHS mid/lower panel and these werent perfect.

End of the day, most of these bikes are 15+ years old, and finding one that hasnt been dropped is going to be very very rare. On the flipside, these bikes (CBR250/RVF400) were built a lot stronger than the plastic shit available nowdays (Ninja 250R), so if they are dropped, its not an instant write-off.