Geoff Candy: Are we likely to see a shortage of supply of these sorts of denominations.
Bernhard Schnellmann: A shortage yes, but that's not because of the metal, it's just because of the minting capacity. You have to same situations of the four coins - if the bullion coin - if we are sold out it's not because there is not enough gold around but also because there are not enough minting presses around.
If you believe there will be increased mass market demand for gold going forward and like your minted coins or bars, then stock up now because you will face premium increases and/or rationing. Once that happens small cast bars will be the other economical option and I think it would be a while before industry capacity is maxed out for them.
I would also draw attention to Bernhard's comment that being sold out does not indicate that "there is not enough gold around". The "selling out" of retail size coins and bars is an indicator of mass market demand and is bullish, but it is not an indicator of no gold. If you see any commentator claiming this, then the only thing it is indicating is that the commentator has no precious metals industry experience on the physical side and in my view any basic commercial sense, in which case you should consider carefully any of their other claims. It is a very good indicator of a hype merchant rather than someone trying to give you good advice.