This is a genuine vintage vest, made in England by Lena Lastik, in the early 1930s or possibly 1920s.
It buttons all the way down the front, and has long sleeves with stretchy ribbed cuffs.
The colour is a creamy white.
This is unsold shop stock, and has been in storage at the shop for at least half a century.
There is a hand-written shop tag attached - this has a pencilled decimal price, presumably added in the 1970s.
Lena Lastik were active in the early part of the 20th century.
Their advertising slogans included:
The Wonder Wear of Underwear
Economical Durable Unshrinkable
It is difficult to date these garments precisely, but they appear to be pre-war.
Size: One size: OS - roughly UK size 16-18
The material is very stretchy.
The unstretched measurement straight across the bust is 18".
The back is 23" long.
This garment was made LONG before the days of garment composition labels and garment care instructions.
The material appears to be all cotton (except for the cuffs).
I would suggest hand-washing, and drying flat, would be the safest garment care - but it might be wise to consult a specialist.