This coin type, as well as the “sister type" 1935-LB, has a most interesting history. 1935-no-L has low mintage of only 175,000 and is one of the scarcer Vreneli years, whereas 1935-LB was minted in a quantity of over 20 million. You can read all about it here in an article in PDF format found on the
Swiss Mint website.
Unfortunately, it seems to be available only in German. But I will translate the relevant parts here for you:

THE VRENELI LOSES ITS CURRENCY VALUE:
“As a result of the worldwide Great Depression, most countries started to devaluate their currencies in 1931. Things began to look critical for Switzerland in 1936 when France, as practically the last of the major economic powers at the time, also devaluated their currency. This caused the Swiss Federal Council to pass a decree on Sept. 27, 1936 devaluating the Swiss Franc by approximately 30%. This was based on the existing fiscal emergency laws.

“Gold parity with the Swiss Franc was adjusted such that one Franc was redeemable at between 190-215 mg of fine gold (formerly 290 mg), and the Swiss National Bank (SNB) was relieved of their obligation to redeem paper money in gold. Although they were not officially removed from circulation, the gold coins immediately lost their convertibility at face value since the intrinsic gold value after devaluation was approx. 28 Francs. Gold Vreneli coins thus became a commodity and were predominantly hoarded by the population after this act.

POSTWAR COINAGE FROM 1945-1949:
“Between February 1945 and April 1947, gold Vreneli coins were struck to satisfy the rising demand for gold coins, but also to reduce the swollen gold surplus which had been acquired during the war by the SNB.

“In order to signify compliance with the new laws of 1936 and to show that they contained the required quantity of fine gold, these coins were struck with the year ‘1935’. Also, it was hoped that speculation as to the source of the gold would be silenced. In order to disambiguate these coins from those actually struck in 1935, the date was prefixed with the letter ‘L’ (for ‘Lingot’, or bar). Until early 1947, only gold bars which could be proven to have been already in possession of the SNB by 1939 were used for striking these coins. In early 1947, however, the pre-war gold reserves were exhausted. Afterwards, the SNB used post-war gold, including some Russian reserves. By then about 20 million 20 Franc gold Vreneli coins had been minted with the date ‘L 1935’ [NB: the ‘B’ stands for Berne, the city of the actual mintmark].

“The Swiss Federal Council decided in March 1947 to discontinue the somewhat controversial practice of pre-dating the coins and decided to leave off the ‘L’. The Washington Agreement of 25 May 1946 supposedly allowed the use of gold acquired from the Deutsche Reichsbank during the war for the minting of coins. Coins were now struck with their true year; compliance with the Coinage Act of 1931 was indicated by the edge inscription: ‘*****AD / LEGEM ANNI / MCMXXXI*’. At the end of 1949, the emergency fiscal laws went out of force, and no more Vreneli coins were minted.”