The SLF, meanwhile, announced its first exit yesterday, from Aberdeen-based energy services firm Red Spider Technology.
Red Spider announced in December that it had been acquired by US-based oil services giant Halliburton.
Glasgow-based Maven Capital Partners, which runs the public and private sector-funded SLF, said it had received its contractual return from its agreement with Red Spider but did not reveal the terms.
However, Maven investment director David Milroy said it was "very happy" with the return from Red Spider in such a short space of time.
Commercial signage manufacturer Merson has used mezzanine debt from the SLF to help fund its acquisition of the assets and trade of fellow East Kilbride company CGL Systems, a specialist in wall cladding and guttering.
The SLF, established by the Scottish Government to plug a funding gap for companies with growth potential, is providing an initial £900,000 to Merson, with a further commitment enabling the signage maker to draw down as much as £3 million in total.
The purchase of the CGL assets was also backed by a Regional Selective Assistance grant from economic development agency Scottish Enterprise and funding from banking giant HSBC.
Merson is investing to ramp up its manufacturing capacity, and creating 20 jobs in East Kilbride. After the CGL purchase, it has 147 staff at East Kilbride, 53 in England, and five in its Middle Eastern offices of Riyadh, Jeddah and Beirut.
The capacity hike will allow it to bring in-house manufacturing work which it has had to sub-contract.
Mr Milroy said: "They have been trading very well over the past couple of years. They had got to the stage their main manufacturing
site at East Kilbride had no spare capacity. It meant they had to sub-contract that [additional] manufacturing to other companies, which meant they were giving away margin to other businesses."
He added: "All that business they were sub-contracting and giving away margin on, they can bring back in-house. It makes for a much more profitable story."
The latest Companies House filing for Merson Signs, of which managing director Roddy Angus and sales and marketing director Gavin McMurray between them own 60%, shows it raised pre-tax profits to £455,112 in the year to September 30 from £277,521 in the prior 12 months. Turnover climbed from £12m to £15.3m.
The CGL purchase will raise the annual turnover of Merson, which was the subject of a management buy-out from previous owner Bruce Lyle in 2002, to about £25m. The firm was founded in 1938.
Mr Milroy noted Merson's major customers include Lloyds Banking Group, retailers Tesco, Waitrose and John Lewis, vehicle group Volvo, and airports operator BAA. He highlighted Merson's presence and expansion ambitions in Saudi Arabia. He said the SLF finance provided included a "small equity option".