Thanks for your feedback, B!
I am not very sure about placing the following drawings here, because they are not firearms per se:
Some of these hand grenades were best known as weapons used in WWII, specially the Italian "red devils", or the well known German stick grenade. But during the Spanish Civil War, since the beginning in July 1936, hand grenades were used intensely.
Before the war, the spanish army was equipped with a defensive grenade Model 18 with a primitive fusing system, without any safety other than a piece of cotton between the match at the end of the fuse, and the abrasive surface in the interior of the rubber cap. The other reglamentary grenade was a spanish version of the Lafitte offensive grenade, sometimes supplemented by and additional security device in the form of a textile band with a lead weight at one end around the body of the granade, after throwing the grenade, gravity pulls the lead and unwraps the cloth, so the contact fuze is ready to function with a minor contact.
At the republican zone, the Ferrobellum consortium (communist lead) at Madrid made several hand and mortar grenades, and also pistol and rifle ammo. Also at Madrid, the 5th Regiment (also communist lead) was the core of 1st Mixed Brigade and probably the best trained and equiped of the republican militias, had an organization capable not only of recruiting soldiers, but also of financing the war, feeding and giving uniforms to all the ranks of the regiment and even arming them. The hand grenade "5th regiment" was a sample of this: primitive in nature, it was a cast cylinder closed by two metallic sheets bolted together, with a fuse that was inserted prior to be used.
A similar fused was the "Asturias" grenade which was made in the North by the miners of the very leftist Asturias (oftenly called "the red one") and had a cast iron body. One of the most used republican grenade was the Universal Grenade (here is shown the grenade of 6 rows, there was another slightly longer of 8 rows), a copy of a French WWI era grenade it was made also of cast iron, and was equipped with any available fuze: here is depicted with a Spanish made version of the polish fuze. A similar cylindrical grenade was called "de discos": when used with the proper Brilliant fuze, the grenade could be fired from a grenade discharger and the discs of the bottom of the body were the "seal" of the projectile, but when another fuze was used, it only could be thrown by hand. Finally, a dangerous weapon, made by the anarchists FAI factories in Catalonia, was called "La Impracial" (the impartial one) because it killed friends and foes alike (that was due the powerful spring of the safety, even when wrapped by a Lafitte like cloth and lead weight, the spring was so powerful the ignites the grenade prematurely), which was a heavy (almost 3 pounds) and difficult to be thrown by hand to a sabe distance.
In the first year of the war, the republicans ordered a huge amount of polish weapons, among them were the reliable and well liked defensive grenade GR-31, and the offensive grenade GR-33 (which was called "bed ball", due the resemblance of the grenade with the then common end of the bronze ends of the beds). The polish grenades, both offensive and defensive, were very copied in Spain, both body and fuzes. But as the cast body production was faster than the fuze production, any available fuse was used (even the most primitives wick fuses), a good match was the body of a bed ball grenade with a soviet UZRGM like fuse (probably an ancestor of that fuze, as it was introduced only in 1942). This fuzes were standard in the soviet made F1 grenades, which were also very numerous in the republican side.
The francoist side used intensively the hand grenades of italian and German origin (mainly offensive ones, and all the italian were contact-fuzed, instead of the more usual time-fuzed), as well as the reglamentary Tonelete and Lafitte grenades. Cheers.