Market Maker or some exchange we don't know of yet that is playing margin on Stamp (like coinarch on Finex).
Stamp does not offer margin as far as I know. Also, it seems to be giving away money with every trade. Odd behaviour for a market maker ...
Can you say more about coinarch on Finex? I don't know anything about that
EDIT: Coinarch is using Bitfinex for it's trades, it allows only a max of 1000usd per trade, with leverage x2 x3...x10
So at times where the price is a bit stable like now, you see many 1000x10/price_BTC orders (or 1000x5/price_BTC etc)