Our revenue returned to growth, up 5% from a year ago.
Core product revenue was up 12%.
We officially launched LUNAR this spring, and our Q2 results include about $1 million of revenue related to product sales.
In the second quarter, the International segment operating margin rose 70 basis points to 16.5%.
And looking back to Q2 of 2019, segment margin is up more than 350 basis points.
With annual revenue of about $70 million, it's headquartered here in Pittsburgh, not far from our gas detection center of excellence, where we've recently made significant investments.
If we add Bacharach into our quarter end net leverage, the pro forma would be about 1.7 times net.
For 17 years, we've been dedicated to helping protect the world's workers.
This recognition was based on a survey of more than 50,000 employees around the country.
We were also ranked number 16 on the Forbes Best Midsize Employers list, and we were number one for engineering and manufacturing industry category.
We returned to revenue growth in the second quarter with total sales up 5% in constant currency.
Second, our operating margin of 17.2% showed a nice sequential uptick from Q1 despite $4 million of higher stock compensation expense related to our recently announced acquisition and its expected revenue and profitability contributions over the coming years.
The expenses, noncash and negatively impacted operating margin by approximately 130 basis points in the quarter.
We completed the Bacharach acquisition earlier this month for $337 million with an after-tax cost of debt of less than 2%.
Quarterly revenue was up 9%, reaching $341 million.
Revenue was up 5% on a constant currency basis.
While we saw about a 2.5% benefit associated with the addition of Bristol, our APR business presented a 5% headwind on a year-over-year basis.
In constant currency, revenue in the Americas was up 6%, while international revenues were up 3%.
The international performance reflects a lag in vaccine deployment and economic recovery, which is tracking a few months behind the U.S. Core product revenue was up 12% on growth across fire service and industrial PPE, partially offsetting a lower FGFD business.
Looking at industrial PPE, it's great to see the strong growth rates in these areas, upwards of 20% or 30% compared to 2020.
Our FGFD business declined 4% compared to last year on challenging comps in the Middle East.
This has resulted in backlog increasing 15% from the end of Q1, particularly in gas detection products.
SG&A expenses was -- were $83 million or 24.4% of sales and was up $12 million from a year ago in constant currency.
This trend played out as expected and impacted the quarterly comparison in SG&A by about $3 million.
Quarterly SG&A also includes about $8 million of costs related to Bacharach and and Bristol acquisitions, including the stock compensation of about $4 million adjustment that I spoke about previously.
Bacharach transaction costs of about $2 million and the remainder being the Bristol base SG&A.
We expect SG&A to approximate 23.5% of sales for the second half of 2021.
We invested $7 million in restructuring programs in the quarter, primarily in our International segment as we continue to execute on our margin expansion road map.
Together with the programs we had discussed in 2020, we continue to expect to deliver approximately $15 million of savings across the income statement in 2021 and annual savings of $25 million thereafter.
Our quarterly adjusted operating margin was down 150 basis points from a year ago.
International margins were up 70 basis points to 16.5% of sales.
America margins were down 140 basis points to 22.6% of sales.
Variable compensation resets associated with the improved revenue performance drove 140 basis point decline in the quarter.
Our quarterly tax rate was 27.8% on a GAAP basis or 27.4% on an adjusted basis.
First, the statutory tax rate increase in the U.K. from 19% to 25% drove a onetime adjustment to our deferred taxes.
From a cash flow and capital allocation perspective, quarterly free cash flow conversion was more than 100% of net income.
In the second quarter, we paid down $25 million of debt, funded $17 million of dividends to shareholders and invested $11 million in capex programs.
On a pro forma basis, following the acquisition, net debt-to-EBITDA would be 1.7 times compared to 0.6 times at June 30.
We continue to expect Bacharach to provide $0.10 to $0.15 of adjusted earnings per share in the second half of 2021.
In connection with the acquisition, we funded $200 million of 15-year senior notes with a fixed interest rate of 2.69%.
With the pro forma debt for Bacharach, we'd expect interest expense to be in the range of $3.5 million to $4 million in Q3 and Q4 of this year.
We also completed a buyout of our minority partner in our China business for about $19 million in July.
And as part of this deal, we expect to repatriate between $10 million to $15 million of cash back to the U.S. in the third quarter.
Before we move on, let's touch on the adjustment to the product liability reserve, which drove $12 million of expense in the quarter.

Summary:
Quarterly revenue was up 9%, reaching $341 million.