I have a Lodoss OVA cel/sketch with no number but 
comparing it to scene on TV and also checking 
paint against other Lodoss OVA cels I have I am 
99.99% sure its a real production cel.

On your Kenshin cel, if cann't find screencap of 
cel might check it against episode cel collection 
bookcover it looks like it is from.  Could be 
real, but there are also some Kenshin repro cels 
floating around from Korean studio who did some 
unauthorized repros.