* March sales up 0.4 pct; Reuters survey +0.3 pct
* Constant-dollar sales +0.5 pct
* New orders -19.9 pct, largest fall at least since 1992
* Unfilled orders -0.8 pct; +15.4 pct in Feb (Adds effects of revisions, paragraphs 7-8)
OTTAWA, May 15 (Reuters) - Canadian manufacturing sales rose in March, by 0.4 percent, for the third straight month and the sixth time in the last seven months, and registered a gain of 3.5 percent from a year earlier, Statistics Canada said on Thursday.
Sales rose to a post-recession high of C$50.92 billion ($46.72 billion), the largest since August 2008.
The median forecast in a Reuters survey of analysts had been for a 0.3 percent rise from February, though estimates ranged from a 1.0 percent drop to a 1.6 percent climb.
The volume, or constant-dollar value, of sales rose by 0.5 percent.
New orders slumped 19.9 percent, their largest fall since the data series begin in 1992, though Statistics Canada said this was a matter of returning to normal levels after February's 17.6 percent leap, which was fueled mainly by transportation equipment. Unfilled orders fell 0.8 percent after a 15.4 percent jump in February.
Sales rose in food, aerospace, machinery, plastics and rubber products, and computers and electronic equipment, but fell in paper and in petroleum and coal products.
With this report, Statistics Canada also made historical revisions to its data. The combined effect of the revisions and any new information the agency may have received altered the picture of January's supposed rebound from December's weather-induced decline.
In March, the agency had reported a 1.5 percent bounce-back in January from a 1.5 percent fall in December. That has now been revised to a 0.3 percent rise in January after a 0.8 percent fall the month before.
$1=$1.09 Canadian Reporting by Randall Palmer; Editing by Chizu Nomiyama and James Dalgleish