Period Austrian made lighter flints. The flints seem to work well; I opened one packet and tested them. They do seem a little long for most of the lighters I have, but can probably be broken in half (you will likely need pliers). Some of the flints may have degraded a bit as most bags have some powder inside too, but this doesn't have an effect on the usability.
The Treibacher Company produced and sold lighter flints like these and packaged this way this for many decades through WWI and WWII as I can find evidence of these little envelopes from the early 1900's and still the same package in the 1950's. Each flint measures about 3mm in diameter and about 2 cm long. The price is for one packet with about 10 flints inside.