LONDON -- It was an erratic week for the FTSE 100 (INDEX: ^FTSE), as it slumped by 85 points on Tuesday after a strong anti-austerity vote in the Italian election raised fresh eurozone fears. But the index of top U.K. stocks recovered to end the week 43 points up at 6,379 -- still a little short of its Feb. 20 record of 6,412 points. Here are four FTSE 100 stocks that moved significantly during the week.

Weir Group (WEIR 0.85%)
Weir Group stock gained 203 pence (9.4%) to 2,359 pence, in the week the engineering services company reported a 12% rise in full-year pre-tax profit to 443 million pounds. That came from an 11% rise in revenue to 2.54 billion pounds. Earnings per share gained 12% to 150 pence, enabling a 15% boost to the full-year dividend to 38 pence. That's a yield of only 1.7%, but it's heading in the right direction as the company targets double-digit dividend growth each year.

ARM Holdings (ARM)
Chip designer ARM Holdings saw its price surge again this week, reaching a 52-week high of 970.5 pence on Friday before closing the week on 965.5 pence. The stock is up 41.4 pence since the previous Friday, for a 4.5% gain -- and it's up around 70% over the past 12 months. But what of valuation? Forecasts for the year ending December 2013 put the stock on a P/E of over 50, which is well above the current FTSE 100 average of about 16, and there's only a tiny dividend expected. But earnings are expected to grow more than 25% per year for the next two years, and who can say where that will end?

GKN (GKN)
Automobile and airplane parts maker GKN released results on Tuesday, and better-than-expected profits enabled it to lift its 2012 dividend by 20% to 7.2 pence. Sales rose by 13% to 6.9 billion pounds, with adjusted pre-tax profit up 19% to 497 million pounds and earnings per share up 17% to 26.5 pence. Forecasts suggest a flat year for earnings in 2013, but the stock is on an undemanding-looking P/E of 10. The result? A 17.3 pence (6.9%) price rise on the week to 269.4 pence.

Kazakhmys (KAZ)
Kazakhmys, the copper miner with interests in Kazakhstan, lost 29.8 pence (8.2%) to 334.9 pence after the market reacted poorly to its full-year trading update. With copper prices having declined 10% during 2012 and the company facing higher production costs, full-year revenue fell by 5.9% to $3.35 billion and the dividend will be cut by more than half. Copper production for 2013 is anticipated to be in line with 2012, but production costs are expected to rise further. Kazakhmys stock is down more than 40% over the past 12 months.

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