I've just reacquired from my father my first ever airgun, a Slavia 624... Have to say I am chuffed to bits as I thought it was long gone

However it has languished in his workshop for several years, and needed some TLC to say the least...

So today I stripped it, cleaned it, removed rust etc., touched up with a bit of cold blue and rubbed down and oiled the stock. Now it looks as good as it ever will, and shoots nicely too (6 shots in 10mm at 6m ).
However the breech seal is flat as anything and definitely need replacing, so my question is this:

What is the difference (if any) between the 624 and the 625?
Chambers don't have a diagram for the 624, but the 625 looks near on identical - will I be able to use the o-ring breech seal from this in my 624?

I'd be grateful for any advice.

Cheers.