I think the Nickerson air-rifles were one of the Spanish brands, Cometa or Norica.
Some smaller air-rifles are suprisingly accurate because they have low-power mainsprings in them. This means that they do not have much spring-surge and have hardly any recoil, and also the basic trigger mechanisms are not struggling with holding back a heavy spring & can be sweeter than their larger brothers.
If you look carefully, you will probably find your rifle is still being made under a different model name and number.
Viva Espana home of the Nickerson!