Saxon M1845 Faschinenmesser
Crown over JR is for King Johann, 1854-1873
These choppers of this form go back to the 18th century and variants turn up well into the 19th centurry with yet others still around in WWI. Faschine knifes are basically of the military machete role of cuttoing brush and rods to weave breastworks. If you watch Band Of Brothers (it all just ran again today), you'll see trenches lined with rods weaved between uprights to hold back the dirt.
PDL is for the Peter D. Luneschloss Company, in business as an exporter of cutlery and swords. I honestly don't know how long the company was in business but the JR would be within those decades. PDL is often noted in Tiffany sales of the non regulation civil war officer and cavalry swords as well as the iron hilted M1840 aka "wristbreaker" cavalry sword.
The numbers and letters on the guard would be regimental. I don't know those either but there are a few forums you could visit if someone here doesn't know. Hail/ping the user Germania in the Bernard Levine subsection or the fellows at
www.swordfourm in the A&M section. There are also pages and boards for id but my German is pretty meager.
http://www.deutsches-blankwaffenforum.de/galerie/index.html
These pioneer/artillery and other briquet handle types arefairly common finds.
Cheers
GC