Nimbus Sans No 5
Some of the fonts have history predating Helvetica's first release. For example, Nimbus Sans bold condensed, Nimbus Sans bold condensed (D) were dated 1940; Nimbus Sans Black Condensed, Nimbus Sans Black Condensed (D) were dated 1946. The fonts ending with (D) names have slightly lighter font weights and tighter spacing.
Although the characters are not exactly the same, Nimbus Sans L has metrics almost identical to Helvetica and Arial.