What's the difference in XLI, XLII, and XLV

As I search for a bus, I have come to understand the natural progression in the XL shell from XLI to the XLII. I don't know what all the differences between them are except the break in model years.

But I noticed that there are also XLV. I see these listed in years before and after the model change from XLI to XLII.

Just what is a "XLV" and where does it fit into the Prevost lineup ??

XL is the original 40 foot bus.
XLV is the original riveted bus but 45 feet long
XLII is the new style bonded skin bus.

XLI?????

Thanks Jon. I knew it had to be simple...
There are listings that use the XL-I identifier. I will assume that they really mean XL ??

Here is an example:

http://www.rvonline.com/single-ad.asp?Recnumber=31081

Michael

They can call THAT camper anything they like, very nice. That buffalo pattern is the same as that Liberty that belonged to Randy Travis thats for sale, it was on the couch. That interior is just the right feel for Deb and I!