Ok, I see the cert. or typed Cert. copy that is in the bass. I have never seen anyone put an actual cert. IN the bass. That usually stays in an envelope but this might be a copy.
The Bass on a close-up of the top by the repair shows that it is un-purfled. The varnish is so dark that I can't see the scroll button if it was grafted. I mention this because the neck aria looks slightly raised and could have been a blockless bass. The string length is not on the appraisal inside but I think it is 3/4 sized overall. I do not agree with the 1750-1760 date at all. Maybe it is 100 years or more later, closer to 1900 I would say and that is by the style of the bass. I would consider this a factory/shop made bass and as cheap as they could make them back then for export. Wurlitzer actually sold basses like this that were new and these cheaply constructed basses either looked old on day one or aged at a rapid pace. They were prone to breaking from their blockless type construction. The woods also were probably not well ages not to mention the acclimation of a bass like this once arriving from southern Germany or the Tirol. The tuners are nicer and probably not original but unless I examine the bass in person, I can't say 100% for sure or even if the scroll is original to the bass.
This is not a valuable bass so be careful how much you put into it. There are a few threads about these basses in the 'German School' section.
http://www.smithbassforums.com/showthread.php?t=1408
http://www.smithbassforums.com/showthread.php?t=1331
http://www.smithbassforums.com/showthread.php?t=764
http://www.smithbassforums.com/showthread.php?t=265
These basses due to their construction which in many cases helped them to fail and need many repeirs makes them look older than they are. Appriasials like the one in the bass are often done like that to make the customer think they have something better than what the do actually have. This way the a 'classy' shop like Wurlitzer can charge you a pretty penny for the paper as well as sell you on the repairs it needs. Back then this bass was from $25-$200 new depending on the model, where you bought it (Sears or Wurlitzer or?) and when it was bought being before or after the first war. Repairs could easily exceed its value at any given period of time, then or now.