100% of these patterns that I have used have been impeccably drawn, true to size, and can't be beat on authenticity- you get practically a book of documentation with most patterns. This will be bias cut in a green fabric with textured stripe woven in.
The fabric came from Regency Revisited, http://www.regencyrevisited.com/ . Their selection is far and above what appears on the website and it is owned and operated by two of my favorite people- Jan and Walt Dubbeld.
Examples exist in photographs, art, and extant garments from the middle decades of the 19th Century of waistcoats cut on the bias and made with slanted embroidered designs creating a similar effect. This was done with both striped and plaid designs and with the slant running in either an upward or downward direction. Here is an example of one in the MET dated by the museum to 1835-40 that is embroidered with the slanting lines facing up:
Here is a similar example from the Fashion Museum in Bath, England that they date to the 1840s. Also embroidered but with the pattern facing down:
This fellow from the ca. 1840s-50s is wearing what appears to be a bias cut waistcoat in a plaid pattern:
Another example of this from ca. 1849 (from the Daguerrian Society or Eastman House Colloection):
Ca. mid 19th Century (guessing 1850s), bias cut with stripes facing up:
And this fellow from the ca. 1850s with his stripes facing down but not to the center:
They seem to have achieved every possible variation. My stripes will face down and to the center.
The Victorian Man