You didn't give guage info and that would be helpful. As far as info on rarity or function, I can say this, the Lefevers grades are similar to Parkers, ie; the lower grades are more common and less expensive than the higher grades. Again, like Parker, the lower grades are as serviceable and robust as the higher grades, just less embellished. I am speaking to the sideplate models, not the Nitro Specials. Value is determined by the guage, overall condition and originality.
Here's a few on auction.
http://www.gunbroker.com/Auction/Vie...Item=319129233
http://www.gunbroker.com/Auction/Vie...Item=317123510
http://www.gunbroker.com/Auction/Vie...Item=318802810
I hope you get the Lefever. I have one and love it.