I'm also made in Belgium, old and the best parts still OK
When it's an old double then it's strange it carries a name. "Agmearms 60" doesn't ring a bell here.
What's the caliber? Please check the length of the chambers before you shoot them.
And to check it's quality: normally you can find the weigth of the barrels (at date of production) on the underside of the barrel. It says something as 1 Kg 460, meaning this barrel weighted 1,460 kg when new. A simple scale (and for you some calculation from lbs to kg) will tell you if it's worn and/or cut shorter.
And don't worry: these guns were made to shoot, I'm still shooting them occasionally (and it's great fun, sure when you reload using blackpowder).
Don't use steel shot with them, they survived lead till now so don't ruin them for political reasons.
When you give the marks they put on the barrels, I'll try to look up how old etc. it is. We have a rather long tradition in teststamps.
And just 1 correction in your statement: don't worry about it's looks, it doesn't have to look OK to shoot OK and to love it.