These included boxers who would hold world championship titles, among them Louis "Kid" Kaplan, Frankie Klick, Bud Taylor, and Tommy Paul as well as British and Canadian champion Al Foreman and accomplished Americans Eddie Mack and Harry Forbes.

[2] On 3 January 1930, Holtzer defeated future junior lightweight world champion American Frankie Klick at Hollywood's Legion Stadium in a ten-round points decision.

[5] Fighting the skilled American world lightweight contender, Eddie Mack, on 25 February 1930, at Los Angeles's Olympic Stadium, Holtzer lost in a close ten round points decision.

Fighting with his rushing style, crouching defense and carefully placed deceptive blows, Holtzer retained more energy in the closing rounds where he nearly overtook his opponent's lead, and the decision for Mack was booed at the end by the crowd.

[6] In an impressive win, Holtzer defeated former World bantamweight champion Bud Taylor in a ten round bout that was the main event on 10 November 1930 in Los Angeles.

[7] In an early career loss on 30 June 1930, Holtzer fell to former World featherweight champion Louis "Kid" Kaplan in a ten-round points decision at West Springfield, Massachusetts.

[10] Winning in a ten round points decision at Olympic Stadium in Los Angeles on 14 October 1930, Holtzer defeated Goldie Hess, a boxer who would face some of the greatest lightweights of his era including Tony Canzoneri, Jack "Kid" Berg, and Barney Ross.

[12] On 23 March 1931, Holtzer lost to Italian American Tommy Paul, a future World featherweight champion, in a tenth round unanimous decision at the Arena in Philadelphia.

[2] Fighting one of his most accomplished opponents in one of his most unexpected victories, Holtzer defeated American Freddie Miller, the reigning World featherweight champion, on 11 February 1935 in a ten-round points decision at the Palais de Sports, in Paris.

[19] He successfully defended both his EBU European and French Featherweight titles on 11 January 1936 against Georges LePerson in a 13-round TKO at the Central Sporting Club in Paris.

[2] Holtzer defended only his EBU European featherweight title on 11 June 1936 by defeating Stan Basta in Brno, Czech, Republic, in a fifteen-round points decision.