In-Service Miniatures was a small company run out of Lakewood, California, during the 1980s and early 1990s. They produced a variety of unique miniatures and specialized in variants of widely available models.
Many items in the ISM line were existing miniatures with camo netting, on-board baggage or sandbags added, hence the name "In Service." Many of their base models (that is, the models without the baggage) resemble those of other manufacturers. I don't know their licensing arrangements (if they had any), but it appears that GHQ and CinC models formed the bases for a few of their models. It appears as though the company was originally called Croissant Miniatures.
The fate of the ISM moulds remains something of a mystery. From various rumors and stories on the net, it seems they were sold off in the early-to-mid 1990s when the manufacturer went out of the business (and moved?). At some point, the molds were sold to someone in Illinois (see the address on several new additions). Reportedly, however, the moulds were in rough shape and production was not resumed. Any other information on this subject would be appreciated.
You can read more information here: Micro Armor Mayhem