I've never opened the envelope so no idea. A couple of weeks later the Buster produced a weekly cut out and fold mini comic with one strip reprinted from each of the past 25 years.
http://www.bustercomic.co.uk/freebies.html
Drat, the above link lists all the free gifts ever given away with Buster, except for possibly a few in 1995. Unfortunately this one is only referred to as Deadly Rattler.
Well, the implication is that they're rattlesnake eggs, but rattlesnakes don't actually lay eggs - they carry them in their body. So I expect it's that practical joke, where, when you open the envelope, a paperclip on a rubber band starts rattling to make you think one's hatched in there.
I remember the merger, and first issue of School Fun well - however, quite a lot of my favourite Buster story's finished including 'Gums', which was a loss.
I haven't opened the envelope on my copy either, but there is HOW TO USE YOUR FREE GIFT instruction on an inside page, so Raven has got it spot on:
Raven wrote:Well, the implication is that they're rattlesnake eggs, but rattlesnakes don't actually lay eggs - they carry them in their body. So I expect it's that practical joke, where, when you open the envelope, a paperclip on a rubber band starts rattling to make you think one's hatched in there.
It seems quite similar in principle to the 'Whampire Bat' given away with an early issue of Wham! I remember that my father nearly had a heart attack when I concealed one of them in his evening newspaper!