Say Spain produced weapons, could anybody afford them back then? I mean, the crowd that can't trade with the US or Soviet that sit on piles of WWII surplus.
In the early to late 50s and on into the 60s, you've got tons of buyers. Remember that no country in Europe was buying from just one other nation after they got back on their feet. Yeah, Israel may have bought Mirages from France, but it still got it's tanks from Britain and America. And alot of it depends on what the Spanish are producing. Actual weapons aren't the only thing to produce. Think of a tank, and all the parts it's made of. Any of those parts can break, and after WWII alot of those parts stopped getting made.
But many countries kept using those tanks. American Shermans, Chaffees, Jacksons, British Cromwells, Comets, Centurions, etc., were all used
decades after WWII: Israeli M-55 Super Shermans made their final bow in 1973, Serbian Jackson tank destroyers were in use in the 90s, and South Africa still uses the Centurion.
These tanks all need spare parts and upgrades. And the fact is, it's not hard to make a sprocket or something for a large machine like a tank. It's pretty similar, I'd think, to making axles and such for combines and tractors. That's what I do for a living now, and it's not rocket science. On top of actual weapons, Spain could make a lot of money just turning out what are called "service parts" for older Allied tank models from the Second World War that are then being used in other armies around the world.
So...say you're a South African ARMSCOR buyer, and your Comet fleet is great except the tank treads are wearing, as well as the transmissions. Along comes a Spanish representative who's willing to do alot more business with you (alot friendlier) than anyone else. And he can offer you something that no one else can: a
new transmission, and new treads.
This gets them in good with their prospective buyers: countries without a lot of money to spend on topshelf military merchandise but who are still looking for a good bang for their buck.
So the Spanish could go to South Africa, say, and make them an offer that includes everything from tank transmissions to AAA guns. Sure, it's not hi-tech stuff, but for where they're selling this stuff to it doesn't need to be.
If you're selling to apartheid South Africa, pre-war South Korea, or any number of other places, then you don't need to offer hi-tech stuff.