The pattern was issued by Patons around 1950, and the knitter made it (I think) for her husband. She left off the patch pockets, but otherwise followed the pattern closely. The waistcoat has obviously been well worn - there's an area on one armhole edge where the cast-off edge has begun to fray.
There seems to have been a fashion for men to wear yellow woollies in the early 1950s - earlier posts showed Roger Moore modelling a yellow pullover and a yellow cardigan. Having said that, I don't believe my father ever wore yellow in his life.
The pattern is titled "Waistcoat Tailored in Knitting" and says "the stitch cleverly reproduces the effect of woven fabric". The fronts of the waistcoat are in linen stitch, which does give a woven effect on the right side, while the reverse resembles moss (or seed) stitch. The back is in single rib, for stretchiness - linen stitch is a very un-stretchy stitch.
If you don't know linen stitch, it's a 2 row pattern. On an even number of stitches: on row 1, (knit 1, bring the yarn to the front, slip 1, take the yarn to the back), and repeat to the last stitch. On row 2, (purl 1, take the yarn to the back (i.e. right side), slip 1, bring the yarn to the front), and repeat to the last stitch. So on each row, you knit alternate stitches and take the yarn across the right side of the fabric when you slip a stitch.
The waistcoat is knitted in 3-ply wool: here's a close-up. I reckon that there are about 12 stitches and 20 rows to the inch. Linen stitch is very dense: not only does it take 2 rows to work all the stitches on the needle, but also slipping stitches has the effect of contracting the work sideways to some extent. The pattern leaflet only gives the tension in stocking stitch: 7½ stitches and 9½ rows to one inch. It says optimistically: "If you knit to the correct tension in stocking stitch, you will knit naturally to the correct tension for any stitch in this book." Really? In linen stitch, I suspect that knitters with the same stocking stitch tension might differ quite a lot in how tight they pull the yarn across each slipped stitch.
So knitting this waistcoat must have taken a very long time. Even when the main part is finished, the button band is knitted separately - 68 inches (1.73 m.) of single rib on 11 stitches, which would be very tedious. And then you have to sew it all on. Altogether a lot of work - but on the other hand, the finished waistcoat has lasted in pretty good condition for 60 years so far.