IT sounds like a success story for Scottish small business, at least on paper.

For the last two years or so a firm in Edinburgh has been supplying some of the fuel powering America’s military might in eastern Europe.

Stonewin Capital, registered just off the capital’s Royal Mile, has secured scores of contracts with US Department of Defence.

There is one problem. There is absolutely no way of knowing who owns the business or how profitable it is. Stonewin Capital is a Scottish limited partnership or SLP, one of thousands created in recent years.

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This is a kind of business still being openly marketed as an “offshore tax-free company” across the old Soviet Union and beyond.

So America’s military, at least partially, is being fuelled by an anonymously owned shell firm. The Herald last month asked the US Department of Defence if it had a policy on doing business with opaque structures. It has been unable to respond.

The US Federal Procurement Data System has some 220 entries for Stonewin Capital contracts for “fuel oils” or “propellant fuels”. This, aside from normal company information, is practically the only digital footprint left by the SLP.

The last contract visible on open source was in November last year. That was several months after the SLP, under emergency rules imposed by the UK Government, was supposed to have named its ultimate beneficiary, or, to use the jargon, person of significant control or PSC.

This is where Stonewin becomes particularly curious for anybody with an interest in how effective Britain’s PSC regime is. That is because the SLP did, initially, appear to comply with the regulations. Public filings at Companies House show that Stonewin Capital declared that its person of significant control was Alexandrs Kolosovs, a Latvian national with an ethnic Russian name.

Two months later it changed its mind.

In another declaration it withdrew its original notification and said it believed it had a PSC, but did not know who that was. The signature on the filing was illegible.

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Stonewin Capital was set up as what appears to be an off-the-shelf shell company in 2014 with two opaque untraceable partners, both in the Pacific’s Marshall Islands.

The US Air Force has been deploying fighters to bases in Estonia and elsewhere on the Russian frontier in recent years.

The Herald understands the contracts with Stonewin Capital may relate to such deployments but the Department of Defence did not comment on this.