Searoam is provided by Base, KPN group who manage the callback product.

It seems that Base have a funky way of calling. With most callback systems there are two legs of a call: the country you are in and the country you are calling to. Each leg costs money. But the Base callback system has 3 legs, all calls go back to the Base hub first and then out. This extra leg means they will never be as cheap as a regular callback system.

But there seems to be one advantage, that is for roaming in those countries that have an Inter-Operator-Tariff, which is a very high levy add to calls and used by some networks in some countries, like the USA. You can call to the USA cheap, but because of the IOT it is very expensive to use it in the USA. The Base system means they can make the IOT rates much cheaper.

One has to weigh up where one travels. If you go to the countries with high IOT charges, then Base is Excellent, but for anywhere else it is expensive. There are only about 20 countries with an IOT, many of them are funky countries that aren't on the beaten track (Except USA and Canada) so for most I dont think it would make sense.

Sorry, when I say Searoam is provided by base, I mean the callback system their product is using is Base. (Maxroam / Celtrek use Base)

The thing that makes Callback a little less reliable then normal calls is the callback trigger and the additional leg (Normal calls only have one leg not two) One could imagine that having an extra leg could cause additional unreliability.

Is there anybody that can help me in knowing this special
Restriction code needed to purchase the sim online?

Yes... this is what it says... and the sentance doesn't even make sense! There is no mention in the T's and C's and no helpful "What is this?" or "help" button to click on next to the requirement. Perhaps it has something to do with this:
(from: SeaRoam - Frequently Asked Questions)
Perhaps you need to send them some digitized ID before you can buy the product. Perhaps they will then send you the restriction code. Who knows?

To me it just demonstrates the customer orientated competence of this company. Personally I wouldn't go near buying a product from them. I am still waiting for a ticket to be resolved from more than a year ago by maxRoam. (same company). Just read through the threads on this forum to see what regular members here think of them...

Hey. Remember who this is actually targeted at.
 

The promoter is some UK [I think] charity that serves 'seafarers'. If you are not a 'seafarer', it is not intended for you.
Not really. They are not seeking 'customers' outside of their mission.

Then why did they come spamming here?

They told me they only sell to sailors thats why their rates are subsidised because sailors are poor is what they told me.

Interesting. I wonder if there really IS a subsidy. Would that make any sense from a business standpoint?

Anyway, their rates have changed, some lower, but many from my list of target countries are higher. USA is now totally not viable at like 1.65$ a minute, some other places in the middle east are also about 50% higher than they were. I really liked the .50$ rate pretty much everywhere, but that seems to be gone.

I gotta say, I think these guys are falling off the list of realistic carriers/cards. I have a trip to Abu Dhabi TOMORROW, and had confirmed on their website AND via email support that there was not only coverage but also confirming their rates - which were UP from their normal .50$ a minute anywhere (that seemed to have changed back in Jan this year.

But, today I check on their site and BOOM Abu Dhabi is now no longer listed and email support says "no coverage" I don't get it, and at this point have no chance to find an alternative.

Fail,

they have quite atrractive rates within europe, eur.0.22/min. on outgoing calls.
SeaRoam - View Our Low Rates

their sim cards are availiable to anyone through their website, not only to seafarers.