The event included a factory tour to look at new developments and a buffet lunch.
Some of the visitors had worked at the company's original premises in Cheadle, Cheshire and many more at the second site in Macclesfield on Charter Way.
The family business currently boasts 6 employees with more than 40 years' service and 10 with 25 years or more.
For more information visit www.sisis.com.
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