Note that just this last week, DNW sold a Seychelles pattern/trial informal set of two coins with 1977 date and J. Mancham obverse. These were never thought to have been issued as he was overthrown as PM and coins all switched to an obverse that features the Republic coat of arms.
Relatively common is a collector silver crown in the 25R denomination that was contracted out evidently before the overthrow, but these are relatively unknown with the only internet searchable results are similar two coin lots sold by DNW in 2014 and 2015 - all six coins are different specimens so not the same lot being re-offerred.
These coins appear much as the KN specimen pieces that have come on market in the last several years but have not yet been able to locate the minting source of these coins.